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06. mathematics arts pm t 9-10 genarel scince [onlinebcs.com]
1.
MATHEMATICS 281 Arts KZ©„K
2016-2020 e¨vsK wcÖwj I wjwLZ cixÿvi cÖ‡kœi c~Y©v½ mgvavb 1. Number System M.C.Q 672. How many integers from 1 to 1000 are divisible by 30 but not by 16? (1 †_‡K 1000 Gi g‡a¨ KZ¸‡jv c~Y©msL¨v 30 Øviv wefvR¨, wKš‘ 16 Øviv wefvR¨ bq?) [Sonali Bank (S.O.-2018); Bangladesh Bank (Officer-2018); Agrani Bank (Officer Cash-2017); Bangladesh Bank (Officer General-2019); Rupali Bank Ltd. (Officer-2019)] a 29 b 31 c 32 d 38 a mgvavb : 30 1000 90 100 90 10 33 1 †_‡K 1000 Gi gv‡S 33wU msL¨v 30 Øviv wefvR¨ GB 33wU msL¨vi gv‡S 16 Øviv wefvR¨ msL¨v¸‡jv n‡e 30 Ges 16 Gi j.mv.¸ ev 240 Gi ¸wYZK 1| 240 1000 960 40 4 1 †_‡K 1000 Gi gv‡S 240 Gi ¸wYZK 4wU| 30 Øviv wefvR¨ wKš‘ 16 Øviv wefvR¨ bq Giƒc msL¨v (33 – 4) ev 29wU| 673. If n is an even integer, which of the following must be an odd integer? (n hw` †Rvo c~Y©msL¨v nq, Zvn‡j wb‡Pi †KvbwU Aek¨B we‡Rvo msL¨v?) [Bangladesh Bank (Officer General-2019)] a n2 – n b n + 2 c 3n – 1 d 3n3 c mgvavb : awi, n = 2 a n2 – n = 22 – 2 = 2, †Rvo b n + 2 = 2 + 2 = 4, †Rvo c 3n – 1 = 3 2 – 1 = 5, we‡Rvo [mwVK DËi] d 3n3 = 3 23 = 24, †Rvo 674. If both x and y are prime numbers, which of the following CANNOT be the product of x and y? (x I y †gŠwjK msL¨v n‡j wb‡Pi †KvbwUÑ x I y Gi ¸Ydj n‡Z cv‡i bv?) [Rupali Bank Ltd. (Officer-2019)] a 6 b 10 c 35 d 27 d mgvavb : Ack‡bi msL¨v¸‡jv‡K `ywU †gŠwjK msL¨vi ¸Ydj AvKv‡i cÖKvk K‡i cvB, (a) 6 = 2 3 (b) 10 = 2 5 (c) 35 = 5 7 (d) 27 = 3 9 †hŠwMK msL¨v mwVK Ackb : d| 675. How many integers from 1 to 100 are divisible by 3 but not by 8? (1 †_‡K 100 ch©šÍ KZ¸‡jv c~Y©msL¨v Av‡Q hviv 3 Øviv wefvR¨ wKš‘ 8 Øviv wefvR¨ bq?) [Combined 5 Banks (Officer-2018)] a 30 b 29 c 31 d 32 b mgvavb : 3 100 33 9 10 9 1 3 Gi ¸wYZK = 33wU 3 I 8 Gi j.mv.¸. = 3 8 = 24 AZGe 24 Øviv wefvR¨ msL¨v¸‡jv 3 I 8 Dfq Øviv wefvR¨| 24 100 4 96 4 24 Øviv wefvR¨ msL¨v = 4wU †gvU msL¨v = 33 – 4 = 29wU 676. After dividing a positive integer y, by 3, the remainder is 2; but when y is divided by 7, the remainder is 4. What is the least possible value of y? (3 Øviv †Kv‡bv c~Y©msL¨v y †K fvM Ki‡j fvM‡kl _v‡K 2| wKš‘ y †K hLb 7 Øviv fvM Kiv nq, ZLb fvM‡kl _v‡K 4| y Gi m¤¢ve¨ me©wb¤œ gvb KZ?) [Sonali & Janata Bank (S.O. IT-2018)] a 11 b 22 c 18 d 32 a mgvavb : Option Check : (a) 11 – 2 = 9; hv 3 Øviv wefvR¨ 11 – 4 = 7; hv 7 Øviv wefvR¨ (b) 22 – 2 = 20; hv 3 Øviv wefvR¨ bq (c) 18 – 2 = 16; hv 3 Øviv wefvR¨ bq (d) 32 – 2 = 30; hv 3 Øviv wefvR¨ 32 – 4 = 28; hv 7 Øviv wefvR¨ wKš‘ †h‡nZz 11 < 32; ZvB mwVK DËi a weKí mgvavb : awi, 3 I 7 Øviv y †K fvM Ki‡j fvMdj nq h_vµ‡g x I z| fvR¨ = fvRK fvMdj + fvM‡kl y = 3x + 2 Ges y = 7z + 4 x I z me©wb¤œ n‡j y Gi gvbI me©wb¤œ n‡e| y = 7z + 4 = (7z + 2) + 2 = 3x + 2 7z + 2 = 3x x = 7z + 2 3 z Gi gvb 1 n‡j (me©wb¤œ) x = 7 1 + 2 3 = 9 3 = 3 A_©vr c~Y©msL¨v nq| x = 3; z = 1 y = 3x + 2 = 3 3 + 2 = 11
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282 PHENOM’S RECENT
BANK SOLUTION 677. If m and p are positive integers and (m + p) m is even, which of the following must be true? (hw` m I p abvZ¥K c~Y©msL¨v nq Ges (m + p)m GKwU †Rvo msL¨v nq, Z‡e wb‡Pi †KvbwU Aek¨B mZ¨?) [Sonali Bank (S.O.-2018)] a If m is odd, then p is odd b If m is odd, then p is even c If m is even, then p is even d If m is even, then p is odd a mgvavb : (m + p) m †Rvo n‡e hw` G‡`i AšÍZ GKwU †Rvo nq| m we‡Rvo n‡j, (m + p) †K †Rvo n‡Z n‡e, †m‡ÿ‡Î p I we‡Rvo n‡Z n‡e| Ackb a mwVK I b fzj| m †Rvo n‡j p Gi gvb †Rvo ev we‡Rvo hvB †nvK bv †Kb (m + p)m †Rvo n‡e| AZGe c I d m¤ú~Y© mwVK e³e¨ bq| mwVK DËi : a 678. What is the probability that an integer selected at random from those between 10 and 100 inclusive is a multiple of 5 or 9? (10 †_‡K 100 Gi g‡a¨ (10 I 100 mn) †_‡K †Kvb c~Y© msL¨v‡K ˆ`ePq‡b wbe©vPb Ki‡j Zv 5 A_ev 9 Øviv wefvR¨ nevi m¤¢ve¨Zv KZ?) [Bangladesh Bank (A.D.-2018)] a 27 89 b 20 91 c 27 91 d 23 89 c mgvavb : 10 †_‡K 100 Gi g‡a¨, 5 Gi ¸wYZK 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 Ges 100 A_©vr 19wU 9 Gi ¸wYZK 18, 27, 36, 45, 54, 63, 72, 81, 90, 99 A_©vr 10wU 9 Ges 5 ¸wYZK 45, 90 †gvU msL¨v = (100 – 10) + 1 = 91wU 5 A_ev 9 Øviv wefvR¨ nevi m¤¢ve¨Zv = 19 91 + 10 91 – 2 91 = 27 91 679. If * is defined for all positive real numbers a and b by a * b = ab (a + b) , then 10 * 2 = ? (mKj abvZ¥K ev¯Íe msL¨vi (a, b) Rb¨ a * b = ab (a + b) n‡j, 10 * 2 = ?) [Bangladesh Bank (Officer-2018)] a 5 3 b 5 2 c 5 d 20 3 a mgvavb : a * b = ab a + b a = 10, b = 2 n‡j, 10 * 2 = 10 2 10 + 2 = 20 12 = 5 3 680. In each expression below, N represents a negative integer. Which expression could have a negative value? (wb‡Pi ivwk¸‡jv‡Z N Øviv GKwU FYvZ¥K c~Y© msL¨v cÖKvwkZ nq| †Kvb ivwkwUi gvb FYvZ¥K n‡Z cv‡i|) [Bangladesh Bank (Officer-2018); Agrani Bank (Officer Cash-2017)] a N2 b 6 – N c – N d 6 + N d mgvavb : awi, N = – 10 (a) N2 = (– 10)2 = 100 > 0 (b) 6 – N = 6 – (– 10) = 16 > 0 (c) – N = – (– 10) = 10 > 0 (d) 6 + N = 6 + (– 10) = – 4 < 0 mwVK DËi d 681. Find the value of : 6 (– 3) 1 3 (– 0.25) [Sonali Bank (Officer-2018)] a 6 b 4.5 c 1.5 d – 0.5 c mgvavb : 6(–3) 1 3 (–0.25) = (–) (–) 6 3 1 3 1 4 = 6 4 = 1.5 682. In m and p are positive integers and m + pm is even, which of the following must be true? (hw` m Ges p abvZ¥K c~Y©msL¨v nq Ges m + pm †Rvo msL¨v nq, wb‡Pi †Kvb Z_¨wU mZ¨?) [Agrani Bank (Officer Cash-2017)] a If m is odd, then p is odd. b If m is odd, then p is even. c If m is even, then p is even. d If m is even, then p is odd. a mgvavb : Avgiv Rvwb, †Rvo msL¨v †Rvo msL¨v = †Rvo msL¨v we‡Rvo msL¨v we‡Rvo msL¨v = we‡Rvo msL¨v we‡Rvo msL¨v †Rvo msL¨v = †Rvo msL¨v we‡Rvo msL¨v + we‡Rvo msL¨v = †Rvo msL¨v we‡Rvo msL¨v + †Rvo msL¨v = we‡Rvo msL¨v †Rvo msL¨v + †Rvo msL¨v = †Rvo msL¨v m p m + pm 1) †Rvo †Rvo †Rvo + †Rvo †Rvo = †Rvo 2) †Rvo we‡Rvo †Rvo + †Rvo we‡Rvo = †Rvo 3) we‡Rvo we‡Rvo we‡Rvo + we‡Rvo we‡Rvo = †Rvo 4) we‡Rvo †Rvo we‡Rvo + we‡Rvo †Rvo = we‡Rvo a, c Ges d wZbwU mwVK| wKš‘ c I d `ye©j Ackb| KviY m †Rvo n‡j, p Gi gvb †Rvo/we‡Rvo hv-B †nvK (m + pm) †Rvo n‡e| wKš‘ m hw` we‡Rvo nq, Z‡e p †K we‡Rvo n‡ZB n‡e| ZvB me‡P‡q mwVK DËi a|
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MATHEMATICS 283 683. In
first 1000 natural numbers, how many integers exist such that they leave a remainder 4 when divided by 7 and a remainder 9 when divided by 11? (cÖ_g 1000 ¯^vfvweK msL¨vi g‡a¨, KZ¸‡jv c~Y©msL¨v Av‡Q hv‡`i 7 w`‡q fvM Ki‡j 4 fvM‡kl _v‡K Ges 11 Øviv fvM Ki‡j 9 fvM‡kl _v‡K?) [B.D.B.L. (S.O.-2017); B.H.B.F.C. (S.O.-2017)] a 11 b 13 c 15 d 17 b mgvavb : 7 Øviv fvM Ki‡j 4 fvM‡kl _v‡K Ggb msL¨v : N = 7x + 4; x = 0, 1, 2, ............ N = 4, 11, 18, 25, ............ 11 Øviv fvM Ki‡j fvM‡kl 9 _v‡K Ggb msL¨v : M = 11Y + 9; Y = 0, 1, 2, ............ M = 9, 20, 31, ............ N = 4, 11, 18, ............ d = 7 M = 9, 20, 31, ............ d = 11 awi, N Gi n Zg I M Gi m Zg c` mgvb| GiKg hZ¸‡jv mgvb c` cvIqv hv‡e, ZZ¸‡jv-B n‡e DËi| 4 + 7(n – 1) = 9 + 11(m – 1) 7(n – 1) – 11(m – 1) = 5 GLb, n – 1 = 7 Ges m – 1 = 4 n‡j Dfqcÿ mgvb n‡e| 7 7 – 11 4 = 5 n – 1 = 7 n = 8 m – 1 = 4 m = 5 G‡ÿ‡Î 1g msL¨vwU n‡e 53 GLb, 53 Gi ci †_‡K we‡ePbv Ki‡j : 53 + 7(n – 1) = 53 + 11 (m – 1) 7(n – 1) = 11(m – 1) 7 11 = 11 7 1g avivq 53 Gi c‡i 11 Ni ci ci Ges 2q avivq 53 Gi 7 Ni ci ci msL¨v¸‡jv mgvb n‡e| n – 1 = 11 m – 1 = 7 n = 12 m = 8 7 1000 142 994 6 H iƒc †gvU msL¨v = 142 11 + 1 = 12 + 1 = 13 (Ans.) 684. If n – 5 is an even integer, what is the next large consecutive even integer? (n – 5 GKwU †Rvo c~Y©msL¨v, cieZ©x eo µwgK †Rvo msL¨vwU KZÑ) [B.H.B.F.C. (S.O.-2017)] a n – 7 b n – 3 c n – 4 d n – 2 b mgvavb : (n – 5) Gi cieZ©x µwgK †Rvo msL¨vwU = n – 5 + 2 = n – 3 2. H.C.F and L.C.M M.C.Q 685. What is the H.C.F of the numbers 36, 54 and 90? [Bangladesh Bank (Officer General-2019)] a 6 b 9 c 12 d 18 d mgvavb : 36 = 2 2 3 3 54 = 2 3 3 3 90 = 2 3 3 5 M.mv.¸. = 2 3 3 = 18 686. The H.C.F. of two numbers is 24. The number which can be their L.C.M. is– (`ywU msL¨vi M.mv.¸. 24| wb‡Pi †KvbwU G‡`i j.mv.¸. n‡Z cv‡i?) [Rupali Bank Ltd. (Officer-2019); Agrani Bank (Officer Cash-2017)] a 84 b 128 c 148 d 120 d mgvavb : `ywU msL¨vi j.mv.¸. Aek¨B Zv‡`i M.mv.¸. Øviv wbt‡k‡l wefvR¨ n‡e| (a) 84 24 = 3 12 24 (b) 128 24 = 5 8 24 (c) 148 24 = 6 4 24 (d) 120 24 = 5 mwVK Ackb : d| 687. The pair of co-prime numbers is– (mn‡gŠwjK †Rvo n‡jvÑ) [Rupali Bank (Officer Cash-2018)] a 2, 3 b 2, 4 c 2, 6 d 2, 110 a mgvavb : †h mKj msL¨vi M.mv.¸ 1 A_©vr 1 Qvov hv‡`i g‡a¨ Avi †Kv‡bv mvaviY Drcv`K †bB, Zv‡`i ci¯úi mn‡gŠwjK msL¨v e‡j| 2, 3 `ywUB †gŠwjK msL¨v hv‡`i M.mv.¸ = 1 2, 4 Gi M.mv.¸ = 2 2, 6 Gi M.mv.¸ = 2 2, 110 Gi M.mv.¸ = 2 (2, 3) mn‡gŠwjK †Rvo| 688. What is the largest number that divides 84, 144 or 18 without any remainder? (†Kvb e„nËg msL¨v Øviv 84, 144 Ges 18 †K fvM Ki‡j †Kvb fvM‡kl _v‡K bv?) [Sonali Bank (Officer-2018)] a 6 b 12 c 18 d 24 a mgvavb : 84, 144 Ges 18 Gi M.mv.¸-B n‡e wb‡Y©q e„nËg msL¨v| 84 = 2 2 3 7 144 = 2 2 2 2 3 3 18 = 2 3 3 wb‡Y©q M.mv.¸ = 2 3 = 6
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284 PHENOM’S RECENT
BANK SOLUTION 689. Find the least number of six digits which is exactly divisible by 15, 21 and 28. (Qq A‡¼i ÿz`ªZg †Kvb msL¨v 15, 21 Ges 28 Øviv wbt‡k‡l wefvR¨Ñ) [B.H.B.F.C. (S.O.-2017)] a 100480 b 100270 c 100380 d 100340 c mgvavb : 15, 21 I 28 Gi j.mv.¸ = 420 6 A‡¼i ÿz`ªZg msL¨v = 100000 420 100000 238 840 1600 1260 3400 3360 40 6 A‡¼i wb‡Y©q ÿz`ªZg msL¨v = 100000 + (420 – 40) = 100380 Written 690. Find the H.C.F. of x3 16x, 2x3 + 9x2 + 4x, 2x3 + x2 28x. (x3 16x, 2x3 + 9x2 + 4x Ges 2x3 + x2 28x Gi M.mv.¸ KZ?) [Agrani Bank Ltd. (S.O. Auditor-2018)] Solution: Given, 1st expression = x3 16x = x(x2 42 ) = x (x + 4) (x 4) 2nd expression = 2x3 + 9x2 + 4x = x(2x2 + 9x + 4) = x{2x2 + 8x + x + 4} = x {2x (x + 4) + 1(x + 4)} = x (x + 4) (2x + 1) 3rd expression = 2x3 + x2 28x = x(2x2 + x 28) = x(2x2 + 8x 7x 28) = x{2x (x + 4) 7(x + 4)} = x(x + 4)) (2x 7) H.C.F (Highest common factor) of given expressions = x(x + 4) 3. Algebra M.C.Q 691. If a2 + 1 a = 3 what is a3 + 1 a3 ? [Bangladesh Bank (Officer General-2019)] a 24 b 7 c 30 d 18 d mgvavb : †`Iqv Av‡Q, a2 + 1 a = 3 a2 a + 1 a = 3 a + 1 a = 3 a + 1 a 3 = 33 a3 + 1 a3 + 3. a. 1 a a + 1 a = 27 a3 + 1 a3 + 3 3 = 27 a3 + 1 a3 = 27 – 9 = 18 692. If a – 1 a = 2 what is a3 – 1 a3? [Rupali Bank Ltd. (Officer-2019)] a 16 b 10 c 14 d 12 c mgvavb : cÖ`Ë ivwk = a3 – 1 a3 = a – 1 a 3 + 3. a. 1 a a – 1 a ‹ x3 – y3 = (x – y)3 + 3xy (x – y) = 23 + 3 2 = 8 + 6 = 14 693. The values of p for equation 2x2 – 4x + p = 0 to have real roots is– (2x2 – 4x + p = 0 mgxKi‡Yi g~j¸‡jv ev¯Íe n‡e hw` p Gi gvbÑ) [Combined 5 Banks (Officer-2018)] a p – 2 b p 2 c p 2 d p – 2 c mgvavb : 2x2 – 4x + p = 0 mgxKiYwU GKwU wØNvZ mgxKiY hv ax2 + bx + c = 0 Gi mgZzj¨ a = 2, b = – 4, c = p ev¯Íe g~‡ji Rb¨ wbðvqK : b2 – 4ac 0 (– 4)2 – 4(2) (p) 0 16 – 8p 0 8 (2 – p) 0 2 – p 0 – (2 – p) 0 [– 1 Øviv ¸Y Kivq AmgZvi w`K cwieZ©b] – 2 + p 0 p 2 694. If a + 1 a = 2 what is a3 + 1 a3 ? (a + 1 a = 2 n‡j a3 + 1 a3 Gi gvb KZ?) [Combined 5 Banks (Officer-2018)] a 1 2 b 7 c 2 d 3 2 c mgvavb : a + 1 a = 2 a3 + 1 a3 = a + 1 a 3 – 3.a. 1 a a + 1 a [‹ x3 + y3 = (x + y)3 – 3xy(x + y)] = 23 – 3 2 = 8 – 6 = 2
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MATHEMATICS 285 695. Bangladeshi
supporters in a stadium double every match. In the eighth match, there were 48000 supporters which was the full capacity of the stadium. In which match did the Bangladeshi supporter fill up half the capacity of the stadium? (GKwU †÷wWqv‡g evsjv‡`kx mg_©K‡`i msL¨v cÖwZ g¨vP AšÍi wظY nq| Aóg g¨v‡P 48000 Rb mg_©K Dcw¯’Z wQj hv †÷wWqv‡gi aviY ÿgZvi mgvb| †Kvb g¨v‡P evsjv‡`kx mg_©K‡`i msL¨v †gvU aviY ÿgZvi A‡a©K wQj?) [Sonali & Janata Bank (S.O. IT-2018)] a 2nd match b 4th match c 6th match d 7th match d mgvavb : 8g g¨v‡P Dcw¯’Z wQj 48000 Rb `k©K hv †÷wWqv‡gi aviY ÿgZvi mgvb| A‡a©K aviY ÿgZv = 48000 2 = 24000 Rb Avevi, cÖwZ g¨vP AšÍi `k©K Dcw¯’wZ wظY nq| A_©vr c~‡e©i g¨v‡Pi Dcw¯’wZ = cieZ©x g¨v‡Pi Dcw¯’wZ 2 7g g¨v‡Pi Dcw¯’wZ = 8g g¨v‡Pi Dcw¯’wZ 2 = 48000 2 = 24000 Rb myZivs 7g g¨v‡P Dcw¯’wZ A‡a©K aviY ÿgZvi mgvb wQj| 696. You bought 11 pencils and erasers worth BDT 80. If erasers cost half that of a pencil and you bought one extra eraser, how much is the eraser worth? (Avcwb 80 UvKv Li‡P †gvU 11wU †cwÝj I B‡iRvi wKb‡jb| cÖwZwU B‡iRv‡ii g~j¨ cÖwZwU †cw݇ji g~‡j¨i A‡a©K Ges Avcwb B‡iRvi GKwU †ewk wKb‡jb (†cwÝj A‡cÿv)| cÖwZwU B‡iRv‡ii g~j¨ KZ?) [Sonali & Janata Bank (S.O. IT-2018)] a 3 b 4 c 5 d 6 c mgvavb : aiv hvK, wZwb †cwÝj wKb‡jb NwU B‡iRvi (N + 1)wU N + (N + 1) = 11 2N = 10 N = 5 myZivs Zuvi µqK…Z †cwÝj = 5wU B‡iRvi = (5 + 1) = 6wU awi, cÖwZwU B‡iRv‡ii g~j¨ x UvKv †cw݇ji 2x UvKv cÖkœg‡Z, 6x + 5 2x = 80 6x + 10x = 80 16x = 80 x = 80 16 x = 5 cÖwZwU B‡iRv‡ii g~j¨ 5 UvKv 697. Jashim buys 10 CDs for BDT 200. If DVDs cost BDT 20 more, how many DVDs can he buy for the same amount? (Rwmg 200 UvKv e¨‡q 10wU CD wKbj| hw` cÖwZwU DVD Gi `vg cÖwZwU CD Gi `v‡gi Zzjbvq 20 UvKv †ewk nq, Z‡e H UvKvq †m KqwU DVD wKb‡Z cvi‡e?) [Sonali & Janata Bank (S.O. IT-2018)] a 4 b 5 c 6 d 10 b mgvavb : 10wU CD Gi g~j¨ 200 UvKv 1wU CD 200 10 = 20 UvKv AZGe, cÖwZwU DVD Gi g~j¨ = (20 + 20) = 40 UvKv 40 UvKvq cvIqv hvq 1wU DVD 1 1 40 DVD 200 200 40 DVD = 5wU DVD 698. The value of k, if (x – 1) is a factor of 4x3 + 3x2 – 4x + k, is– (hw` 4x3 + 3x2 – 4x + k ivwkwUi GKwU Drcv`K (x – 1) nq, Z‡e k Gi gvbÑ) [Sonali Bank (S.O.-2018); Rupali Bank (Officer Cash-2018)] a 1 b 2 c – 3 d 3 c mgvavb : (x – 1) hw` 4x3 + 3x2 – 4x + k Gi GKwU Drcv`K nq, Z‡e x = 1 n‡e 4x3 + 3x2 – 4x + k = 0 mgxKi‡Yi GKwU g~j| 4 13 + 3 12 – 4 1 + k = 0 4 + 3 – 4 + k = 0 k = – 3 weKí mgvavb : awi, (x) = 4x3 + 3x2 – 4x + k (x – 1), (x) Gi GKwU Drcv`K n‡j, (1) = 0 4(1)3 + 3(1)2 – 4(1) + k = 0 4 + 3 – 4 + k = 0 k + 3 = 0 k = – 3 699. If x + 1 x = 3, then x – 1 x = ? (x + 1 x = 3 n‡j, x – 1 x = ?) [Sonali Bank (S.O.-2018)] a 5 b 13 c 7 d 0 a mgvavb : x + 1 x = 3 x + 1 x 2 = 32 x – 1 x 2 + 4x 1 x = 9 [‹ (a + b)2 = (a – b)2 + 4ab] x – 1 x 2 + 4 = 9 x – 1 x 2 = 5 x – 1 x = 5
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286 PHENOM’S RECENT
BANK SOLUTION 700. The factors of x2 – 5x – 6 are : (x2 – 5x – 6 †K Drcv`‡K we‡kølY Ki :) [Sonali Bank (S.O.-2018)] a (x – 6) (x + 1) b (x + 6) (x – 1) c (x – 3) (x + 2) d (x – 3) (x – 2) a mgvavb : cÖ`Ë ivwk = x2 – 5x – 6 = x2 + x – 6x – 6 = x(x + 1) – 6(x + 1) = (x – 6) (x + 1) 701. The roots of the equation 9x2 – bx + 81 = 0 will be equal, if the value of b is (9x2 – bx + 81 = 0 mgxKiYwUi g~j¸‡jv mgvb n‡j b Gi gvbÑ) [Rupali Bank (Officer Cash-2018)] a 9 b 18 c 27 d 54 d mgvavb : 9x2 – bx + 81 = 0 GKwU wØNvZ mgxKiY hv ax2 + px + c = 0 Gi mgZzj¨ a = 9; p = – b; c = 81 wbðvqK = p2 – 4ac g~j¸‡jv mgvb nevi kZ© : p2 – 4ac = 0 (– b)2 – 4 9 81 = 0 b2 = 4 9 81 b = 54 702. How many cases do you need if you have to pack 112 pairs of shoes into cases that each hold 28 shoes? (28wU Ry‡Zv avib Ki‡Z cv‡i Ggb KZ¸‡jv †Km e¨envi K‡i 112 †Rvov Ry‡Zv ivLv hv‡e?) [Bangladesh Bank (Officer-2018)] a 8 b 10 c 12 d 14 a mgvavb : 28wU Ry‡Zv = 28 2 = 14 †Rvov Ry‡Zv| 14 †Rvov Ry‡Zv ivLv hvq 1wU †K‡m 1 1 14 wU 112 112 14 wU = 8wU †K‡m 703. A person needs to pay Tk. 500 to buy pencils and Tk. X for any additional unit of pencil. If the customer pays a total of Tk. 4,700 for 1200 pencils, what is the value of X? (GKRb e¨w³i Kv‡Q 500 UvKv Av‡Q wKQz †cwÝj µq Kivi Rb¨ Ges AviI wKQz †cwÝj †Kbvi Rb¨ x UvKv Av‡Q| hw` e¨w³wU †gvU 1200 †cwÝj wKb‡Z 4700 UvKv e¨q K‡i, Zvn‡j cÖwZwU †cw݇ji g~j¨?) [Sonali Bank (Officer-2018)] a 4.0 b 3.91 c 3.85 d 3.5 b mgvavb : cÖwZwU †cw݇ji g~j¨ = 4700 1200 = 3.91 UvKv 704. If P = 5 + 2 then the value of P2 is– [Sonali Bank (Officer-2018)] a 5 + 10 2 b 20 + 5 2 c 27 + 10 2 d 27 c mgvavb : †`Iqv Av‡Q, p = 5 + 2 p2 = (5 + 2)2 = 52 + 10 2 + 2 = 25 + 2 + 10 2 p2 = 27 + 10 2 705. If x – 1 x = – 3, then x4 + 1 x4 = ? [Agrani Bank (S.O. Auditor-2018)] a 23 b 27 c 3 d 9 a mgvavb : †`Iqv Av‡Q, x – 1 x = – 3 cÖ`Ë ivwk = x4 + 1 x4 = (x2 )2 + 1 x2 2 = x2 + 1 x2 2 – 2 x2 1 x2 = x – 1 x 2 + 2 x 1 x 2 – 2 = { }(– 3)2 + 2 2 – 2 = {5}2 – 2 = 25 – 2 = 23 706. How many real roots does the polynomial 2x3 + 8x – 7 have? (2x3 + 8x – 7 eûc`xi KZwU ev¯Íe g~j Av‡Q?) [Agrani Bank (Officer Cash-2017)] a None b One c Two d Three b mgvavb : awi, (x) = 2x3 + 8x – 7 x –3 –2 –1 0 1 2 3 (x) –85 –39 –17 –7 3 25 71 x = 0 †_‡K x = 1 ch©šÍ (x) Gi gvb –7 †_‡K 3 nq| A_©vr, 0 †_‡K 1 Gi gv‡S eûc`xwUi GKwU ev¯Íe g~j i‡q‡Q| eûc`xwUi 1wU ev¯Íe g~j Av‡Q| weKí mgvavb : – 3 – 2 – 1 1 2 3– 7 – 17 – 39 – 85 25 71 †jLwPÎ n‡Z †`Lv hvq, x = 0 Ges x = 1 Gi g‡a¨ †jLwU x-Aÿ‡K GKevi †Q` K‡i| A_©vr x = 0 Ges x = 1 Gi g‡a¨ GKwU ev¯Íe g~j we`¨gvb|
7.
MATHEMATICS 287 707. The
solutions of 2x2 + 3x – 2 = 0 are [Agrani Bank (Officer Cash-2017)] a x = – 3 and x = 2 b x = 1 2 and x = – 2 c x = – 1 and x = 2 d x = 1 and x = – 2 b mgvavb : 2x2 + 3x – 2 = 0 2x2 + 4x – x – 2 = 0 2x (x + 2) – 1 (x + 2) = 0 (x + 2) (2x – 1) = 0 x + 2 = 0 ev, 2x – 1 = 0 x = – 2 x = 1 2 708. A grocer buys some eggs at Tk. 3 each. He finds that 12 of them are broken, but he sells the others at Tk. 4 each and makes profit of Tk. 96. How many eggs did he buy? (GKRb †`vKvb`vi cÖwZwU wWg 3 UvKv nv‡i wKQz wWg wK‡b| Zvi gv‡S 12wU wWg fv½v wQj, evwK¸‡jv †m cÖwZwU wWg 4 UvKv K‡i weµq K‡i 96 UvKv jvf K‡i| †m KZwU wWg wK‡bwQj?) [B.K.B. (Officer Cash-2017)] a 140 b 142 c 144 d 150 c mgvavb : g‡b Kwi, †`vKvb`vi xwU wWg wK‡bwQj †`vKvb`vi wewµ K‡i (x – 12)wU wWg cÖkœg‡Z, 4(x – 12) – 3x = 96 4x – 48 – 3x = 96 x = 96 + 48 = 144 709. A man buys doughnuts at the rate of Tk. 35 per 100 pieces and sells them at Tk. 7.20 per dozen. If the profit is Tk. 30, how many doughnuts did he buy? (GKRb e¨w³ cÖwZ 100 wcm †WvbvU 35 UvKv nv‡i wK‡b Ges cÖwZ WRb 7.20 UvKv nv‡i weµq K‡i| hw` jvf 30 UvKv nq, Zvn‡j KZ¸‡jv †WvbvU wK‡bwQj?) [B.K.B. (Officer Cash-2017)] a 60 b 120 c 180 d 210 b mgvavb : 1 WRb ev 12wU †Wvbv‡Ui weµqg~j¨ 7.20 UvKv 1wU 7.20 12 100wU 7.20 100 12 = 60 UvKv 100wU †Wvbv‡U jvf = 60 – 35 = 25 UvKv 25 UvKv jvf nq 100wU †Wvbv‡U 30 100 25 30wU †Wvbv‡U = 120wU †Wvbv‡U 710. If x2 – 7xy + y2 is divided by x – 2y, the result is– [B.D.B.L. (S.O.-2017)] a 3x + 2y b 3x – 2y c 2x – 3y d 2x + 3y c mgvavb : cÖkœwU‡Z x2 – 7xy + y2 Gi cwie‡Z© 2x2 – 7xy + 6y2 n‡e| 2x2 – 7xy + 6y2 = 2x2 – 4xy – 3xy + 6y2 = 2x (x – 2y) – 3y (x – 2y) = (x – 2y) (2x – 3y) 2x2 – 7xy + 6y2 x – 2y = (x – 2y) (2x – 3y) (x – 2y) = (2x – 3y) 711. If x – 1 x = 3 then x + 1 x = ? [B.H.B.F.C. (S.O.-2017); B.D.B.L. (S.O.-2017)] a 3 3 b 7 c 2 3 d 7 b mgvavb : †`Iqv Av‡Q, x – 1 x = 3 Gme, x + 1 x 2 = x – 1 x 2 + 4. x. 1 x = ( 3)2 + 4 = 3 + 4 x + 1 x 2 = 7 x + 1 x = 7 Written 712. Factorize: x3 – 21x + 20. [Rupali Bank Ltd. (Officer-2019)] Solution: x3 – 21x + 20 = x3 – x2 + x2 – x – 20x + 20 = x2 (x – 1) + x (x – 1) – 20(x – 1) = (x – 1) (x2 + x – 20) = (x – 1) (x2 + 5x – 4x – 20) = (x – 1) {x(x + 5) – 4 (x + 5)} = (x – 1) (x + 5) (x – 4) 713. If a q r = b r p = c p q then show that, a + b + c = pa + qb + rc [Bangladesh Development Bank Ltd. (SO)-2018] Solution: Given, a q r = b r p = c p q Let, a q r = b r p = c p q = k a = k(q r), b = k(r p) and c = k(p q) L.H.S = a + b + c = k(q r)+ k(r p) + k(p q) = k{q r + r p + p q} = k 0 = 0 R.H.S = pa + qb + rc = pk(q r) + qk((r p) + rk (p q) = k{pq pr + qr pq + pr qr} = k 0 = 0 L.H.S = R.H.S
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288 PHENOM’S RECENT
BANK SOLUTION 714. What should be the values of a and b for which 64x3 9ax2 + 108x b will be a perfect cube? [Bangladesh Krishi Bank Ltd. (Officer Cash-2018)] Solution: We know, (p q)3 = p3 3p2 q + 3pq2 q3 Given expression = 64x3 9ax2 + 108x b comparing, p3 = 64x3 p3 = (4x)3 p = 4x Ges 3p2 q = 9ax2 3 (4x)2 q = 9ax2 q = 9ax2 48x2 = 3a 16 Ges 3pq2 = 108x 3 4x 3a 16 2 = 108x 12x 9a2 256 = 108x a2 = 108x 256 12x 9 = 256 a = 16 Ges b = q3 = 3a 16 3 = 3 16 16 3 = 27 715. Resolve into factors : a2 + 1 a2 + 2 2a 2 a [Bangladesh Krishi Bank Ltd. (Officer Cash-2018)] Solution: a2 + 1 a2 + 2 2a 2 a = a + 1 a 2 2.a. 1 a + 2 2 a + 1 a = a + 1 a 2 2 + 2 2 a + 1 a = a + 1 a 2 2 a + 1 a = a + 1 a a + 1 a 2 (Ans.) 716. Simplify : 5x + 2 x2 x 20 + 2x 1 x2 4x 5 [Agrani Bank Ltd. (S.O. Auditor-2018)] Solution:Given expression 5x + 2 x2 x 20 + 2x 1 x2 4x 5 = 5x + 2 x2 5x + 4x 20 + 2x 1 x2 5x + x 5 = 5x + 2 x(x 5) + 4(x 5) + 2x 1 x(x 5) + 1(x 5) = 5x + 2 (x 5) (x + 4) + 2x 1 (x 5) (x + 1) = (5x + 2) (x + 1) + (2x 1) (x + 4) (x 5) (x + 4) (x + 1) = 5x2 + 5x + 2x + 2 + 2x2 + 8x x 4 (x 5) (x + 4) (x + 1) = 7x2 + 14x 2 (x 5) (x + 4) (x + 1) (Ans.) 717. If a = xyp 1 , b = xyq 1 , c = xyr 1 and p + q + r = 3, then prove that aq r × br p × cp q = 1 [Agrani Bank Ltd. (Officer Cash-2018); Rupali Bank Ltd. (Officer Cash-2018)] Solution: Given, a = xyp 1 , b = xyq 1 , c = xyr 1 and p + q + r = 3 L.H.S = aq r br p cp q = ( )xyp 1 q r ( )xyq 1 r p ( )xyr 1 p q = xq r .y(p 1) (q r) xr p . y(q 1) (r p) xp q .y(r 1) (p q) = xq r + r p + p q ypq pr q + r yqr pq r + p yrp rq p + q = x0 ypq pr q + r + qr pq r + p + rp rq p + q = x0 y0 = 1 = R.H.S (Showed) 718. Find the value of x6 + 1 x6 , if x + 1 x = 3 [Sonali Bank Ltd. (Officer)-2018] Solution: Given, x + 1 x = 3 Given expression x6 + 1 x6 = (x3 )2 + 1 x3 2 = x3 + 1 x3 2 2.x3 . 1 x3 = x + 1 x 3 3.x. 1 x x + 1 x 2 2 = {(3)3 3 3}2 2 = {27 9}2 2 = 182 2 = 324 2 = 322 (Ans.) 719. Simplify : x 1 x2 x 20 + 4 x x2 4x 5 [Combined 5 Bank (Officer)-2018] Solution:Given expression, x 1 x2 x 20 + 4 x x2 4x 5 = x 1 x2 5x + 4x 20 + 4 x x2 5x + x 5 = x 1 x(x 5) + 4(x 5) + 4 x x(x 5) + 1(x 5) = x 1 (x 5) (x + 4) + 4 x (x 5) (x + 1) = (x 1) (x + 1) + (4 x) (x + 4) (x 5) (x + 4) (x + 1) = x2 1 (x 4) (x + 4) (x 5) (x + 4) (x + 1) = x2 1 (x2 42 ) (x 5) (x + 4) (x + 1) = x2 1 x2 + 16 (x 5) (x + 4) (x + 1) = 15 (x 5) (x + 4) (x + 1)
9.
MATHEMATICS 289 4. Equation M.C.Q 720.
If xy = 2 and xy2 = 16, what is the value of x? [Bangladesh Bank (Officer General-2019)] a 4 b 2 c 1 4 d 8 c mgvavb : †`Iqv Av‡Q, xy = 2 x2 y2 = 4 ......... (i) Ges xy2 = 16 ...................... (ii) (i) (ii) x2 y2 xy2 = 4 16 x = 1 4 721. If y x = 1 3 and x + 2y = 10 then x is– [Rupali Bank Ltd. (Officer-2019)] a 2 b 3 c 4 d 6 d mgvavb : y x = 1 3 y = x 3 x + 2y = 10 x + 2 3 x = 10 5x 3 = 10 x = 3 10 5 x = 6 722. How many real roots does the equation 2x3 + 8x – 7 = 0 have? (2x3 + 8x – 7 = 0 eûc`x mgxKi‡Y ev¯Íe gyj KZwU?) [Rupali Bank Ltd. (Officer-2019)] a None b One c Two d Three b mgvavb : †h‡nZz mgxKiYwU wÎNvZ, ZvB G‡Z ev¯Íe g~j _vK‡e 1wU ev 3wU| †Kbbv RwUj g~j¸‡jv AbyeÜx AvKv‡i _v‡K| ZvB RwUj g~‡ji msL¨v 2wU ev GKwU I bq| awi, g~j¸‡jv r1, r2, r3 r1 + r2 + r3 = 0 r1 r2 + r2 r3 + r3 r1 = 8 2 = 4 (r1 + r2 + r3)2 = r1 2 + r2 2 + r3 2 + 2 (r1 r2 + r2 r3 + r3 r1) r1 2 + r2 2 + r3 2 + 2 4 = 0 r1 2 + r2 2 + r3 2 = – 8 wKš‘ KZ¸‡jv ev¯Íe msL¨vi e‡M©i †hvMdj KL‡bvB ïY¨ (0) A‡cÿv †QvU n‡Z cv‡i bv| ZvB r1, r2 I r3 wZbwUB ev¯Íe bq| kZ©vbyhvqx, G‡`i g‡a¨ 2wU RwUj g~j| ev¯Íe g~‡ji msL¨v =1| 723. If xy = 2 and xy2 = 8, what is the value of x? (xy = 2 I xy2 = 8 n‡j x Gi gvb KZ?) [Rupali Bank Ltd. (Officer-2019)] a 4 b 2 c 1 2 d 8 c mgvavb : xy2 = 8 (xy)2 x = 8 22 x = 8 [ xy = 2] x = 4 8 x = 1 2 724. If 3x – 7y = 0 and x + 2y = 13 then y is– (hw` 3x – 7y = 0 Ges x + 2y = 13 nq, Z‡e y Gi gvbÑ) [Combined 5 Banks (Officer-2018)] a 2 b 3 c 4 d 7 b mgvavb : 3x – 7y = 0 ......... (i) x + 2y = 13 .......... (ii) (ii) 3 – (i) 3x + 6y = 39 3x – 7y = 0 (–) (+) (–) 13y = 39 y = 39 13 y = 3 725. A bag and a book costs BDT 1100. If the bag costs 1000 more than the book, how much does the book cost? (GKwU e¨vM I GKwU eB‡qi g~‡j¨i mgwó 1100 UvKv| hw` e¨v‡Mi g~j¨ eB‡qi g~j¨ A‡cÿv 1000 UvKv †ewk nq, Z‡e eB‡qi g~j¨ KZ?) [Sonali & Janata Bank (S.O. IT-2018)] a 100 b 150 c 50 d 200 c mgvavb : awi, eB‡qi g~j¨ = x UvKv e¨v‡Mi g~j¨ = (x + 1000) UvKv cÖkœg‡Z, eB‡qi g~j¨ + e¨v‡Mi g~j¨ = 1100 x + (x + 1000) = 1100 2x = 100 x = 50 eB‡qi g~j¨ 50 UvKv 726. If a + 2b = 6 and ab = 4 what is 2 a + 1 b ? (hw` a + 2b = 6 Ges ab = 4 nq, Z‡e 2 a + 1 b Gi gvb KZ?) [Sonali Bank (S.O.-2018); Sonali Bank (Officer-2018)] a 1 2 b 1 c 3 2 d 2 c mgvavb : a + 2b = 6 ......... (i) ab = 4 .............. (ii) (i) (ii) a + 2b ab = 6 4 = 3 2 1 b + 2 a = 3 2 2 a + 1 b = 3 2
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290 PHENOM’S RECENT
BANK SOLUTION 727. If y x = 3 7 and x + 2y = 13 then y is– [Bangladesh Bank (A.D.-2018)] a 2 b 3 c 4 d 7 b mgvavb : y x = 3 7 x = 7 3 y Avevi, x + 2y = 13 7 3 y + 2y = 13 7y + 6y 3 = 13 13y = 13 3 y = 3 728. If Kabir loses 8 pounds, he will weigh twice as much as his sister. Together they now weigh 278 pounds. What is Kabir’s present weight, in pounds? (hw` Kwei 8 cvDÛ IRb nvivq, Zvi IRb Zvi †ev‡bi IR‡bi wظY n‡e| GLb `yB R‡bi GK‡Î IRb 278 cvDÛ| Kwe‡ii eZ©gvb IRb) [Sonali Bank (Officer-2018)] a 147 b 188 c 135 d 139 b mgvavb : awi, Kwe‡ii eZ©gvb IRb = x cvDÛ Kwe‡ii †ev‡bi eZ©gvb IRb = (278 – x) cvDÛ cÖkœg‡Z, x – 8 = 2 (278 – x) x – 8 = 556 – 2x 3x = 564 x = 188 729. A man spent 1 2 of his money and then lost 1 4 of the remainder. He was left with Tk. 3,600. How much did he start with? (GKRb e¨w³ Zvi UvKvi 1 2 Ask LiP K‡i Ges evwK UvKvi 1 4 Ask nvwi‡q †d‡j| Zvi Kv‡Q 3600 UvKv _vK‡j †m KZ UvKv wb‡q ïiæ K‡iwQjÑ) [Sonali Bank (Officer-2018)] a Tk. 7,200 b Tk. 8,800 c Tk. 9,600 d Tk. 10,400 c mgvavb : g‡b Kwi, e¨w³wUi Kv‡Q x UvKv wQj| LiP K‡i = x Gi 1 2 = x 2 UvKv evwK UvKv = x – x 2 = x 2 UvKv nvwi‡q †d‡j = x 2 Gi 1 4 = x 8 UvKv evwK UvKv = x 2 – x 8 = 4x – x 8 = 3x 8 UvKv cÖkœg‡Z, 3x 8 = 3600 3x = 3600 8 x = 9600 UvKv 730. The population of a certain town increases by 50% every 50 years. If the population in 1950 was 810, in what year was the population 160? (†Kv‡bv kn‡ii RbmsL¨v 50 eQ‡i 50% e„w× cvq| 1950 mv‡j RbmsL¨v 810 n‡j, †Kvb mv‡j RbmsL¨v 160 wQj?) [Agrani Bank (Officer Cash-2017)] a 1650 b 1800 c 1700 d 1750 d mgvavb : g‡b Kwi, x mv‡j RbmsL¨v 160 wQj (x + 50) mv‡j RbmsL¨v = 160 + 160 Gi 50% = 160 + 80 = 240 (x + 50 + 50) ev (x + 100) mv‡j RbmsL¨v = 240 + 240 Gi 50% = 240 + 240 50 100 = 360 (x + 100 + 50) ev (x + 150) mv‡j RbmsL¨v = 360 + 360 Gi 50% = 360 + 360 50 100 = 540 (x + 150 + 50) ev (x + 200) mv‡j RbmsL¨v = 540 + 540 Gi 50% = 810 cÖkœg‡Z, x + 200 = 1950 x = 1750 731. At the beginning of a class period, half of the students in a class go to the library. Later in the period, half of the remaining students go to the computer lab. If there are 8 students remaining in the class, how many students were originally in the class? (†Kv‡bv K¬v‡mi ïiæ‡Z A‡a©K wkÿv_x© jvB‡eªix‡Z hvq| K¬v‡mi gv‡S evwK wkÿv_x©‡`i A‡a©K Kw¤úDUvi j¨v‡e hvq| Ae‡k‡l 8 Rb wkÿv_x© K¬v‡m _v‡K| †gvU wkÿv_x© msL¨v KZ wQj?) [Agrani Bank (Officer Cash-2017)] a 12 b 16 c 24 d 32 d mgvavb : awi, wkÿv_x© msL¨v wQj x Rb K¬v‡mi ïiæ‡Z jvB‡eªix‡Z hvq = x Gi 1 2 Rb = x 2 Rb evwK wkÿv_x© = x – x 2 = x 2 Rb c‡i Kw¤úDUvi j¨v‡e hvq = x 2 Gi 1 2 = x 4 Rb cÖkœg‡Z, x – x 2 + x 4 = 8 x – 2x + x 4 = 8 4x – 3x 4 = 8 x = 32 Rb
11.
MATHEMATICS 291 Written 732. 2n
– 1 + 2n + 1 = 320 n‡j n Gi gvb KZ? [Bangladesh Bank (Recruitment Test-2020)] Solution: 2n – 1 + 2n + 1 = 320 2n – 1 + 2n – 1 + 2 = 320 2n – 1 + 2n – 1 22 = 320 2n – 1 + 4 2n – 1 = 320 5 2n – 1 = 320 2n – 1 = 64 2n – 1 = 26 n – 1 = 6 n = 7 733. Solve : x 2 + 6 y = 9, x 3 + 2 y = 4 [Bangladesh Development Bank Ltd. (SO)-2018; Rupali Bank Ltd. (Officer Cash) Cancelled-2018] Solution: x 2 + 6 y = 9 ................... (i) x 3 + 2 y = 4 (ii) (i) (ii) 3 x 2 + 6 y = 9 x + 6 y = 12 () () () x 2 x = 3 x 2x 2 = 3 x 2 = 3 x = 6 putting value of x in equation .... (i) 6 2 + 6 y = 9 3 + 6 y = 9 6 y = 6 y = 6 6 = 1 (x, y) (6, 1) (Ans.) 734. Price of 3 tables and 5 chairs is Tk. 2,000. Again, price of 5 tables and 7 chairs is Tk. 3,200. What is the price of 1 table and 1 chair? (3wU †Uwej Ges 5wU †Pqv‡ii g~j¨ 2000 UvKv| Avevi 5wU †Uwej Ges 7wU †Pqv‡ii g~j¨ 3200 UvKv| 1wU †Uwej Ges 1wU †Pqv‡ii g~j¨ KZ?) [Bangladesh Krishi Bank Ltd. (Officer Cash-2018); Rupali Bank Ltd. (Officer Cash-2018)] Solution: Let, Price of 1 Table = x Tk and Price of 1 chair = y Tk According to question, 3x + 5y = 2000 ... ... (i) 5x + 7y = 3200 ... ... (ii) (i) 5 (ii) 3 15x + 25y = 10000 15x + 21y = 9600 () () () 4y = 400 y = 100 Putting value of y in equation ... ... (i) 3x + 5 100 = 2000 3x =1500 x = 500 Price of 1 table = 500 Tk and Price of 1 chair = 100 Tk 735. A working couple earned a total of Tk. 43,520. The wife earned Tk. 640 per day, the husband earned Tk. 560 per day. If the total number of days worked by both was 72, formulate a system of equation and solve the system to find the number of days worked by each. (GK Kg©Rxex `¤úwZ †gvU 43520 UvKv DcvR©b K‡i| ¯¿x 640 UvKv cÖwZw`b Avq K‡i Ges ¯^vgx 560 UvKv cÖwZw`b Avq K‡i| hw` Df‡q wg‡j 72 w`b KvR K‡i| GKwU mgxKiY MVb K‡i †K KZw`b KvR K‡i Zv wbY©q Ki?) [Agrani Bank Ltd. (Officer Cash-2018)] Solution: Total working days = 72 Let, husband worked for x days wife worked for (72 x) days According to question, 560 x + (72 x) 640 = 43520 560x + 46080 640x = 43520 46080 43520 = 80x 80x = 2560 x = 32 days husband worked for 32 days wife worked for (72 32) = 40 days 736. Solve : x 2 + y 3 = 1, x 3 + y 2 = 1 [Agrani Bank Ltd. (Officer Cash-2018)] Solution: x 2 + y 3 = 1 .................... (i) x 3 + y 2 = 1 ................... (ii) (i) 2 (ii) 3 x + 2y 3 = 2 x + 3y 2 = 3 () () () 2y 3 3y 2 = 1 4y 9y 6 = 1 5y = 6 y = 6 5
12.
292 PHENOM’S RECENT
BANK SOLUTION Putting value of y in equation ... (i) x 2 + 6 5 3 = 1 x 2 + 6 5 1 3 = 1 x 2 + 2 5 = 1 x 2 = 1 2 5 x 2 = 3 5 x = 6 5 (x, y) 6 5 6 5 737. Amin has 12 pieces of Tk. 10 and Tk. 5 notes in his wallet. If the total value of all the notes is less than Tk. 95, what is the maximum number of Tk. 10 notes that he has? (Avwg‡bi Kv‡Q 10 UvKv Ges 5 UvKvi †gvU 12wU †bvU Av‡Q| hw` †gvU UvKvi cwigvY 95 Gi †P‡q Kg nq| m‡e©v”P KZwU 10 UvKvi †bvU _vK‡Z cv‡i?) [Sonali Bank Ltd. (Officer)-2018] Solution: As, total notes = 12 Let, Number of 10 Tk notes = x ,, ,, 5 Tk ,, = (12 x) According to the question 10x + 5(12 x) < 95 10x + 60 5x < 95 5x < 35 x < 7 Maximum number of 10 taka notes will be = 6 738. Solve the equation : 3 x + 2 + x 1 x 5 = 2 [Sonali Bank Ltd. (Officer)-2018] Solution: Given equation, 3 x + 2 + x 1 x 5 = 2 3 x + 2 = 2 x 1 x 5 = 2x 10 x + 1 x 5 3 x + 2 = x 9 x 5 3(x 5) = (x + 2) (x 9) 3x 15 = x2 9x + 2x 18 3x 15 = x2 7x 18 x2 7x 18 3x + 15 = 0 x2 10x 3 = 0 We know, Solve of this equation ax2 + bx + c = 0 x = b b2 4ac 2a Comparing this equation with ax2 + bx + c = 0 a = 1, b = 10, c = 3 x = ( 10) ( 10)2 4 1 ( 3) 2 1 = 10 100 + 12 2 = 10 112 2 = 10 16 7 2 = 10 4 7 2 = 2(5 2 7) 2 x = 5 2 7 (Ans.) 739. Four students contributed to a charity drive and the average amount contribution by each student was BDT 20. If no student gave more than BDT 25, what is the minimum amount that any student could have contributed? (4 Rb QvÎ GKwU `vZe¨ ms¯’vq `vb Ki‡jv Ges M‡o mevB 20 UvKv K‡i w`‡jv| †Kv‡bv QvÎB 25 UvKvi †ewk †`q bv| GKRb QvÎ me©wb¤œ KZ UvKv w`‡q‡Q?) [Sonali & Janata Bank Ltd. (SO) IT/ICT-2018] Solution: 1 student contributes 20 Tk 4 ,, ,, (4 20) Tk = 80 Tk No student gives, more than 25 Tk Let, out of 4 students, 3 students give 25 Tk Total contribution of 3 students = 3 25 = 75 UvKv minimum amount that any student can contribute = 80 75 = 5 Tk 740. A school has 40 rooms that can sit 600 people. Some rooms can sit 10 people and some can sit 20 people. What is the ratio of the number of 10 person rooms to the number of 20 person rooms? (GKwU ¯‹z‡j 600 Rb e¨w³i Rb¨ 40wU Kÿ Av‡Q| wKQz K‡ÿ 10 Rb Ges wKQz K‡ÿ 20 Rb em‡Z cv‡i| 10 R‡bi Kÿ Ges 20 R‡bi K‡ÿi AbycvZ KZ?) [Sonali & Janata Bank Ltd. (SO) IT/ICT-2018] Solution:Let, Number of 10 seated room = x ,, ,, 20 ,, ,, = (40 x) According to the question, 10x + 20 (40 x) = 600 10x + 800 20x = 600 200 = 10x x = 20 Number of 10 seated room = 20 ,, ,, 20 ,, ,, = 40 20 = 20 Ratio = 20 : 20 = 1 : 1
13.
MATHEMATICS 293 741. A
teacher has 3 hours to grade all the papers submitted by the 35 students in her class. She gets through the first 5 papers in 30 minutes. How much faster does she have to work to grade the remaining papers in the allotted time? (GKRb wkÿ‡Ki 35 Rb wkÿv_x©i LvZv †`Lvi Rb¨ 3 NÈv mgq Av‡Q| cÖ_g 5wU LvZv †`L‡Z 30 wgwbU mg‡q jv‡M| eivÏK…Z mg‡q LvZv †`Lv †kl Ki‡Z KZ `ªæZ LvZv †`L‡Z n‡e?) [Sonali Bank Ltd. (SO) IT/ICT-2018] Solution: To grade first 5 papers the teacher takes 30 minutes or, 30 60 hours or 1 2 hours Now, The teacher takes 1 2 hours to grade 5 papers ,, ,, ,, 1 ,, ,, ,, 10 ,, speed of grading = 10 papers/hour Remaining alloted time = 3 1 2 = 2.5 hours Remaining papers to grade = 35 5 = 30 In 2.5 hours the teacher has to grade 30 papers ,, 1 ,, ,, ,, ,, ,, ,, 30 2.5 ,, = 12 papers speed has to be = 12 papers/hour percentage of speed has to be increased ` = 12 10 10 100% = 20% 742. Solve : x2 yx = 7, y2 + xy = 30 [Sonali Bank Ltd. (SO) IT/ICT-2018] Solution: x2 yx = 7 ................ (i) y2 + xy = 30 ............. (ii) (i) + (ii) x2 + y2 = 37 ........... (iii) From (i), x2 7 = yx y = x2 7 x = x2 x 7 x y = x 7 x ............................. (iv) Putting the value of y in equation (iii) x2 + x 7 x 2 = 37 x2 + x2 2.x. 7 x + 7 x 2 = 37 2x2 14 + 49 x2 = 37 2x2 + 49 x2 = 51 2x4 + 49 x2 = 51 2x4 + 49 = 51x2 2x4 51x2 + 49 = 0 2x4 49x2 2x2 + 49 = 0 x2 (2x2 49) 1 (2x2 49) = 0 (x2 1) (2x2 49) = 0 x2 1 = 0 or, 2x2 49 = 0 x2 = 1 x2 = 49 2 x = 1 x = 7 2 From equation (iv), if x = 1, y = 1 7 1 = 6 if x = 1, y = (1) 7 (1) = 6 if x = 7 2 , y = 7 2 7 7 2 = 7 2 7 2 7 = 7 2 2 = 7 2 2 = 5 2 if x = 7 2 , y = 7 2 7 7 2 = – 7 2 + 7 2 7 = – 7 2 + 2 = 7 + 2 2 = 5 2 So, (x, y) (1, 6), (1, 6), 7 2 5 2 , 7 2 5 2 809. A car owner buys petrol at Tk. 75, Tk. 80 and Tk. 85 per liter for three successive years. What approximately is the average cost per liter of petrol if he spends Tk. 40,000 each year in this concern? (GKRb Mvoxi gvwjK cici wZb eQi 75 UvKv, 80 UvKv Ges 85 UvKv w`‡q †c‡Uªvj wK‡b| †m cÖwZ eQi †gvU 40000 UvKv LiP Ki‡j, M‡o cÖwZ wjUv‡i KZ LiP n‡qwQj?) [Combined 5 Bank (Officer)-2018] Solution: Amount of petrol used in 1st year = 40000 75 = 1600 3 liter ,, ,, ,, ,, ,, 2nd year = 40000 80 = 500 liter ,, ,, ,, ,, ,, 3rd year = 40000 85 = 8000 17 liter
14.
294 PHENOM’S RECENT
BANK SOLUTION Total amount of petrol used in 3 years = 1600 3 + 500 + 8000 17 liter = 27200 + 25500 + 24000 51 liter = 76700 51 liter And, total cost in 3 years = 3 40000 = 120000 Average cost = 120000 76700 51 = 120000 51 76700 = 79.79 Taka 743. A family has 480kg of rice for X number of weeks. If they need to use the same amount for 4 more weeks, they need to cut down their weekly assumption of rice by 4 kg. What is the value of X? (GKwU cwiev‡ii X mßv‡ni Rb¨ 480 kg Pvj Av‡Q| hw` H Pvj Av‡iv 4 mßvn †ewk e¨envi Ki‡Z Pvq, Zv‡`i mvßvwnK Lvev‡ii cwigvY 4 kg Kgv‡Z n‡e| X Gi gvb KZ?) [Rupali Bank Ltd. (Officer Cash-2018)] Solution: As, X is number of weeks and 480 kg is quantity of rice per week consumption = 480 x kg If 4 weeks is to be increased than (x + 4) is number of weeks Again, per week consumption = 480 x + 4 kg According to question, 480 x 480 x + 4 = 4 480 (x + 4) 480x x(x + 4) = 4 480x + 1920 480x x(x + 4) = 4 1920 = 4x2 + 16x x2 + 4x 480 = 0 x2 + 24x 20x 480 = 0 x(x + 24) 20(x + 24) = 0 (x 20) (x + 24) = 0 So, x 20 = 0 or, x + 24 = 0 x = 20 x = 24 but number of weeks can't be negative. 744. 1 2x + 6 y = 3, 5 x + 3 y = 11 [Rupali Bank Ltd. (Officer Cash-2018)] Solution: Given equations, 1 2x + 6 y = 3 ......... (i) 5 x + 3 y = 11 ........ (ii) (i) (ii) 2 1 2x + 6 y = 3 10 x + 6 y = 22 () () () 1 2x 10 x = 19 1 20 2x = 19 19 2x = 19 2x = 1 x = 1 2 Putting value of x in equation (i) 1 2 1 2 + 6 y = 3 1 + 6 y = 3 6 y = 2 y = 3 (x, y) 1 2 3 5. Series M.C.Q 745. The sum of first 17 terms of the series 5, 9, 13, 17, — is– (5, 9, 13, 17 — avivwUi cÖ_g 17 c‡`i mgwó—) [Bangladesh Bank (Officer General-2019); Sonali Bank (S.O.-2018); Agrani Bank (Officer Cash-2017)] a 529 b 462 c 629 d 523 c mgvavb : d = 9 – 5 = 13 – 9 = 4 avivwU mgvšÍi aviv hvi cÖ_g c`, a = 5 mvaviY AšÍi, d = y 17wU c‡`i mgwó = n 2 {2a + (n – 1)d} = 17 2 {2 5 + (17 – 1) 4} = 17 2 {10 + 64} = 17 2 74 = 629 746. The next number in the sequence 3, 6, 11, 18, 27, — is– [Sonali Bank (S.O.-2018); Bangladesh Bank (Office General-2019); Rupali Bank Ltd. (Officer-2019)] a 34 b 36 c 38 d 40 c mgvavb : cÖ`Ë avivwU : 3, 6, 11, 18, 27 27 + 11 + 3 + 5 + 7 + 9 9 + 2 ev + 11 ev 38 + 2 + 2 + 2 + 2 cieZ©x c` = 27 + 11 = 38
15.
MATHEMATICS 295 747. The
next number in the sequence 3, 4, 8, 17, 33, ... is (3, 4, 8, 17, 33, ......... avivwUi cieZ©x c` KZ?) [Combined 5 Banks (Officer-2018)] a 54 b 56 c 58 d 60 c mgvavb : 8 17 33 58 42 52 3 4 22 32 12 748. The second and third terms of a geometric series are 9 and 3 respectively. The fifth term of the series is– (†Kv‡bv R¨vwgwZK ev ¸‡YvËi avivi wØZxq I Z…Zxq c` h_vµ‡g 9 I 3| avivwUi cÂg c`Ñ) [Combined 5 Banks (Officer-2018)] a 1 b 1 9 c 1 3 d 1 27 c mgvavb : awi, cÖ_g c` = a mvaviY AbycvZ = r n Zg c`, Tn = arn – 1 wØZxq c`, T2 = ar2 – 1 = ar Z…Zxq c`, T3 = ar3 – 1 = ar2 cÖkœg‡Z, ar = 9 ................... (i) ar2 = 3 ................. (ii) (ii) (i) ar2 ar = 3 9 r = 1 3 (i) bs G r Gi gvb ewm‡q, a 1 3 = 9 a = 27 cÂg c`, T5 = ar4 T5 = 27 1 3 4 T5 = 27 34 = 33 34 T5 = 1 3 749. n C1 + n C2 + n C3 + ... n Cn = ? [Combined 5 Banks (Officer-2018)] a 2n b 2n – 1 c n(n – 1) (n2 + 1) 2 d 2n – 1 d mgvavb : (1 + x)n = n C0 + n C1x + n C2x2 + .... + n Cnxn (1 + x)n = 1 + n C1x + n C2x2 + n C3x3 + .... + n Cnxn x = 1 n‡j, (1 + 1)n = 1 + n C1 + n C2 + n C3 + .... + n Cn 2n = 1 + n C1 + n C2 + .... + n Cn n C1 + n C2 + .... + n Cn = 2n – 1 750. A person buys a TV worth BDT 3,90,000 with a down payment of 40,000, including Tk. 5000 as first month’s installment. How many more installments does he have to pay if his installments had to double after each successive payment? (GKRb e¨w³ cÖ_g gv‡mi 5000 UvKv wKw¯Ímn GKKvjxb 40000 UvKv cÖ`vb K‡i 390000 UvKvi GKwU TV µq K‡ib| hw` cÖ‡Z¨K gvm AšÍi wKw¯Íi cwigvY wظY nq, Z‡e Zuv‡K AviI KZwU wKw¯Í cwi‡kva Ki‡Z n‡e?) [Sonali & Janata Bank (S.O. IT-2018)] a 6 b 7 c 8 d 10 a mgvavb : TV wUi g~j¨ = 390000 UvKv cÖ_g gv‡mi wKw¯Ímn cwi‡kvaK…Z g~j¨ = 40000 UvKv evwK UvKv = (390000 – 40000) UvKv = 350000 UvKv cÖkœg‡Z, cÖ_g gv‡mi wKw¯Í 5000 UvKv n‡j cieZ©x gv‡m 10000, Zvi c‡ii gv‡m 20000 Ges Gfv‡e Pj‡Z _vK‡e| 10000 + 20000 + 40000 + ......... = 350000 evgcv‡ki avivwUi cÖ_g c`, a = 10000 mvaviY AbycvZ, r = 2 [wظY n‡”Q] hw` cieZ©x n gvm a‡i wKw¯Í cwi‡kva Ki‡Z nq, Z‡e H n gv‡mi wKw¯Íi mgwó = a(rn – 1) r – 1 cÖkœg‡Z, a(rn – 1) r – 1 350000 10000 (2n – 1) 2 – 1 350000 2n – 1 35 2n 36 n = 5 n‡j, 25 = 32 < 36 n = 6 n‡j, 26 = 64 > 36 Zuv‡K AviI 6 gvm wKw¯Í cwi‡kva Ki‡Z n‡e| weKí mgvavb : cÖ_g gv‡mi wKw¯Ímn 40000 UvKv cÖ`v‡bi ci evwK UvKv = (390000 – 40000) = 350000 UvKv cieZ©x n gv‡m H UvKv †kva Ki‡Z n‡j, cÖkœg‡Z, 5000 2 + 5000 2 2 + .... = 350000 a = 2 5000 = 10000 r = 2 arn – 1 r – 1 350000 10000 (2n – 1) 350000 2n – 1 35 2n 36 2n 32 + 4 2n 25 + 4 n > 5; AZGe n = 5 + 1 = 6 gvm
16.
296 PHENOM’S RECENT
BANK SOLUTION 751. 6, 7, 9, 13, __, __. What are the two missing numbers in the series? [Sonali & Janata Bank (S.O. IT-2018)] a 21, 37 b 17, 21 c 21, 39 d 17, 19 a mgvavb : 9 13 21 37 23 =8 24 =16 6 7 2=21 4=22 1=20 752. How many terms of Arithmetic Progression (A. P.) 21, 18, 15, 12, ... must be taken to give the sum zero? (21, 18, 15, 12, ...... mgvšÍi avivwUi KZ msL¨K c‡`i mgwó k~Y¨ n‡e?) [Sonali Bank (S.O.-2018)] a 10 b 15 c 22 d 27 b mgvavb : mgvšÍi avivwUi cÖ_g c`, a = 21 mvaviY AšÍi, d = 18 – 21 = – 3 awi, n msL¨K c‡`i mgwó = 0 n msL¨K c‡`i mgwó = n 2 {2a + (n – 1)d} cÖkœg‡Z, n 2 {2a + (n – 1)d} = 0 {2a + (n – 1)d} = 0 [n 0] 2 21 + (n – 1) (– 3) = 0 3(n – 1) = 2 21 n – 1 = 2 21 3 n – 1 = 14 n = 15 753. After being dropped a certain ball always bounces back to 2 5 of the height of its previous bounce. After the first bounce it reaches a height of 125 inches. How high (in inches) will it reach after its fourth bounce? (GKwU we‡kl ej f‚wg‡Z covi ci me©`v Gi c~‡e©i D”PZvi 2 5 ¸Y D”PZvq jvwd‡q I‡V| cÖ_g evi f‚wg‡Z cZ‡bi ci GwU 125 Bw I‡V| PZz_© evi cZ‡bi ci GwU KZ D”PZvq DV‡e?) [Sonali Bank (S.O.-2018)] a 20 b 8 c 5 d 3.2 b mgvavb : cÖ_g evi cZ‡bi ci I‡V 125 Bw wØZxq Ó Ó Ó Ó 2 5 125 Bw = 50 Bw Z…Zxq Ó Ó Ó Ó 2 5 50 Bw = 20 Bw PZz_© Ó Ó Ó Ó 2 5 20 Bw = 8 Bw weKí mgvavb : cÖ‡Z¨KwU cZ‡bi ci ejwUi DÌvb c~‡e©i 2 5 ¸Y nq| ZvB GB DwÌZ D”PZv¸‡jv GKwU ¸‡YvËi aviv hviÑ cÖ_g c`, a = 125 mvaviY AbycvZ, r = 2 5 PZz_© c` = arn – 1 = 125 2 5 4 – 1 = 125 2 5 3 = 125 8 125 = 8 PZz_© cZ‡bi ci ejwU 8 Bw DV‡e| 754. If a + 1, 2a + 1, 4a – 1 are in Arithmetic Progression then the value of ‘a’ is : (hw` a + 1, 2a + 1, 4a – 1 mgvšÍi avivq _v‡K, Z‡e 'a' Gi gvbÑ) [Rupali Bank (Officer Cash-2018)] a 1 b 2 c 3 d 4 b mgvavb : mgvšÍi avivi c`¸‡jvi exRMvwYwZK e¨eavb mgvb _v‡K hv‡K mvaviY AšÍi e‡j| cÖkœg‡Z, mvaviY AšÍi = (2a + 1) – (a + 1) = (4a – 1) – (2a + 1) a = 2a – 2 a = 2 755. In a series of 6 consecutive odd numbers if 15 is the 6th number, what is the 4th number in the series? (6wU µwgK we‡Rvo msL¨vi 6th msL¨vwU 15 n‡j, H avivi 4th msL¨vwU KZ?) [Bangladesh Bank (A.D.-2018); B.K.B. (Officer Cash-2017)] a 7 b 9 c 11 d 13 c mgvavb : awi, cÖ_g we‡Rvo msL¨vwU a msL¨v¸‡jv a, a + 2, a + 4, a + 6, a + 8, a + 10| 6th msL¨vwU = a + 10 a + 10 = 15 a = 5 4th msL¨vwU = a + 6 = 5 + 6 = 11 756. Which number logically follows the sequence? 4 6 9 6 14 6 ... (†Kvb msL¨vwU 4, 6, 9, 6, 14, 6 ... avivwUi cieZx© msL¨v?) [Bangladesh Bank (Officer-2018)] a 6 b 17 c 19 d 21 c mgvavb : †Rvo ¯’v‡bi msL¨v¸‡jv A_©vr wØZxq, PZz_©, lô, .... c`¸‡jv 6| Avgv‡`i mßg c` †ei Ki‡Z n‡e, hv we‡Rvo ¯’v‡bi c` we‡Rvo ¯’vbxq c`¸‡jv: myZivs, mwVK c`wU 19| cÖ_g Z…Zxq cÂg mßg 4 + 5 9 + 5 14 + 5 19
17.
MATHEMATICS 297 757. The
next number of the sequence is– 4 3 9 3 19 3 ... [Bangladesh Bank (A.D.-2018)] a 31 b 32 c 39 d 49 c mgvavb : 4 3 9 3 19 3 39 5 52=10 102=20 758. In a row in the theatre the seats are numbered consecutively from T1, to T50, Sumon is sitting in seat T17 and Shajib is sitting in seat T39. How many seats are there between them? (GKwU bvU¨kvjvi GK mvwi Avmb‡K cici T1 †_‡K T50 ch©šÍ µwgK EaŸ©µ‡g wPwýZ Kiv Av‡Q| mygb I mRxe h_vµ‡g T17 I T39 bs Avm‡b e‡m‡Q| `yR‡bi gv‡S KZ¸‡jv Avmb Av‡Q?) [Bangladesh Bank (Officer-2018)] a 23 b 21 c 22 d 20 b mgvavb : T17 I T39 Gi ga¨eZx© Avmb¸‡jv n‡jv: T18, T19, T20, .... T37, T38 †gvU Avmb msL¨v = (38 – 18 + 1)wU = 21wU 759. In the given series, which number will come next : 91, 86, 76, 61, —? [Sonali Bank (Officer-2018)] a 31 b 36 c 41 d 46 c mgvavb : 91 86 76 61 – 5 –10 –15 cieZx© msL¨v = 61 – 20 = 41 760. If the first and sixth term of a geometric series are respectively 1 2 and 1 64 , then the common ratio is– (†Kv‡bv ¸‡YvËi avivi cÖ_g I lô c` h_vµ‡g 1 2 Ges 1 64 n‡j, mvaviY AbycvZÑ) [B.D.B.L. (S.O.-2017)] a 1 4 b 1 2 c 1 d 2 b mgvavb : ¸‡YvËi avivi n Zg c` = arn–1 †hLv‡b, a = cÖ_g c`, r = mvaviY AbycvZ GLb, cÖ_g c` a = 1 2 n = 6 Zg c` = 1 2 r6 – 1 = 1 2 r5 cÖkœg‡Z, 1 2 r5 = 1 64 r5 = 1 32 r5 = 1 2 5 r = 1 2 761. The sum of fourth and twelfth term of an arithmetic progression is 20. What is the sum of the first fifteen terms of that arithmetic progression? (GKwU mgvšÍi avivi 4_© Ges 12Zg c‡`i †hvMdj 20| avivwUi cÖ_g 15 c‡`i mgwóÑ) [B.H.B.F.C. (S.O.-2017)] a 300 b 120 c 150 d 130 c mgvavb : mgvšÍi avivi 1g c` a Ges mvaviY AšÍi d n‡j, PZz_© c` = a + (4 – 1)d = a + 3d Ges 12 Zg c` = a + (12 – 1)d = a + 11d cÖkœg‡Z, a + 3d + a + 11d = 20 2a + 14d = 20 ...................(i) GLb, cÖ_g 15 c‡`i mgwó = 15 2 {2a + (15 –1)d} = 15 2 {2a + 14d} = 15 2 20 [(i) n‡Z gvb ewm‡q] = 150 Written 762. `yB A¼wewkó †hmKj msL¨v 3 Øviv wefvR¨ Zv‡`i †hvMdj wbY©q Kiæb| [Bangladesh Bank (Recruitment Test-2020)] Solution: 3 Øviv wefvR¨ `yB As‡Ki msL¨v¸‡jv n‡jv : 12, 15, 18, 21, 24, ......... 90, 93, 96, 99 †hvMdj, S = 12 + 15 + 15 + 18 + ....... + 96 + 99 hv GKwU mgvšÍi avivi mgwó †hLv‡bÑ cÖ_g c`, a = 12 †kl c` = 99 mvaviY AšÍi, d = 3 [15 – 12 =18 – 15 = 96 – 99 = 3] †gvU Giƒc msL¨v n n‡j 99 = a + (n – 1)d 99 = 12 + 3(n – 1) 3(n – 1) = 87 n – 1 = 29 n = 30 s = n 2 (cÖ_g c` + †kl c`) = 30 2 (12 + 99) = 15 111 = 1665 763. Two numbers x, y and in G.P and their sum is 30. Also, the sum of their squares is 468. Find the numbers. (`yBwU msL¨v x Ges y ¸‡YvËi aviv‡Z Av‡Q Ges Zv‡`i mgwó 30| msL¨v؇qi e‡M©i mgwó 468| msL¨vØq KZ?) [Rupali Bank Ltd. (Officer-2019)] Solution: Given, x + y = 30 x = 30 – y .... (i) Again, x2 + y2 = 468 (30 – y)2 + y2 = 468 900 – 60y + y2 + y2 = 468 2y2 – 60y + 900 – 468 = 0 2y2 – 60y + 432 = 0 y2 – 30y + 216 = 0 y2 – 18y – 12y + 216 = 0 y (y – 18) – 12(y – 18) = 0 (y – 18) (y – 12) = 0 y = 12, 18 If, y = 12, x = 30 – 12 = 18 y = 18, x = 30 – 18 = 12 Numbers are 12, 18.
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298 PHENOM’S RECENT
BANK SOLUTION 764. The sum of three numbers in Arithmetic Progression is 30, and the sum of their squares is 318. Find the numbers. (GKwU mgvšÍi avivi 3wU msL¨vi mgwó 30 Ges Zv‡`i e‡M©i †hvMdj 318 msL¨v wZbwU KZ?) [Bangladesh Krishi Bank Ltd. (Officer Cash-2018)] Solution: Let, first term of series = a 2nd term = a + d d is common difference and, 3rd term = a + 2d According to question, a + a + d + a + 3d = 30 3a + 3d = 30 a + d = 10 a = 10 d ... (i) Again, a2 + (a + d)2 + (a + 2d)2 = 318 (10 d)2 + (10 d + d)2 + (10 d + 2d)2 = 318 From (i) 100 20d + d2 + 100 + (10 + d)2 = 318 200 20d + d2 + 100 + 20d + d2 = 318 2d2 + 300 = 318 2d2 = 18 d2 = 9 d = 3 From equation (i) If d = 3, a = 10 3 = 7 d = 3, a = 10 (3) = 13 For, d = 3 and a = 7 1st term = 7 2nd term = 7 + 3 = 10 3rd term = 7 + 3 2 = 13 For d = 3 and a = 13 1st term = 13 2nd term = 13 3 = 10 3rd term = 13 3 2 = 7 Three numbers are 7, 10, 13 765. Prove that the sum of the odd numbers from 1 to 125 inclusive is equal to the sum of the odd numbers from 169 to 209 inclusive. (cÖgvY Ki †h, 1 †_‡K 125 Gi g‡a¨ we‡Rvo msL¨v¸‡jvi †hvMdj 169 †_‡K 209 Gi g‡a¨ we‡Rvo msL¨v¸‡jvi †hvMd‡ji mgvb|) [Agrani Bank Ltd. (Officer Cash-2018)] Solution: Sum of odd numbers from 1 to 125 1 + 3 + 5 + ... + 125 First term a = 1, common difference d = 3 1 = 2 Last term or nth term = 125 a + (n 1)d = 125 1 + (n 1)2 = 125 1 + 2n 2 = 125 2n = 126 n = 63 Now, Sum of n terms = n 2 {2a + (n 1)d} ,, ,, 63 ,, = 63 2 {2 1 + (63 1) 2} = 63 2 {2 + 124} = 63 63 = 3969 Sum of odd numbers from 169 to 209 169 + 171 + 173 + ...... + 209 Here, first term a = 169, common difference d = 171 169 = 2 nth term = 209 a + (n 1)d = 209 169 + (n 1) 2 = 209 2n 2 = 40 2n = 42 n = 21 Sum of 4 terms = 21 2 {2 169 + (21 1) 2} = 21 2 {338 + 40} = 21 2 378 = 3969 1 + 3 + 5 + .... + 125 = 169 + 171 + ... + 209 6. Set M.C.Q 766. If A = {1, 2, 3, 4, 5}, then the number of proper subsets of A is– (A = {1, 2, 3, 4, 5} Zvn‡j A Gi cÖK…Z Dc‡mU KZwUÑ) [Bangladesh Bank (Officer General-2019); Rupali Bank Ltd. (Officer-2019); Sonali Bank (S.O.-2018); Agrani Bank (Officer Cash-2017)] a 120 b 30 c 31 d 32 c mgvavb : A = {1, 2, 3, 4, 5} A †m‡U Dcv`vb msL¨v n = 5 Avgiv Rvwb, n m`m¨wewkó †Kv‡bv †m‡Ui cÖK…Z Dc‡mU msL¨v = 2n – 1| cÖK…Z Dc‡mU = 2n – 1 = 25 – 1 = 31 767. In a group of 60 people, 27 like coke and 42 like borhani and each person likes at least one of the two drinks. How many people like both coke and borhani? (60 Rb e¨w³i GKwU MÖæ‡c 27 Rb †KvK I 42 Rb †evinvwb cQ›` K‡i Ges cÖ‡Z¨‡KB `ywUi AšÍZ GKwU cQ›` K‡i| KZRb e¨w³ †KvK Ges †evinvwb `y‡UvB cQ›` K‡i?) [Sonali & Janata Bank (S.O. IT-2018)] a 9 b 129 c 69 d 15 a mgvavb : †gvU e¨w³, n(S) = 60 †KvK cQ›` K‡i Ggb e¨w³i msL¨v, n(C) = 27 †evinvwb cQ›` K‡i Ggb e¨w³i msL¨v, n(B) = 42 †KvK I †evinvwb Dfq cQ›` K‡i, Ggb e¨w³i msL¨v, n(C B) = ? †h‡nZz cÖ‡Z¨‡KB †Kv‡bv bv †Kv‡bv cvbxq cQ›` K‡i ZvB, AšÍZ GKwU cQ›` K‡i Ggb e¨w³i msL¨v, n(C B) = †gvU e¨w³i msL¨v, n(S) = 60 n(C B) = n(C) + n(B) – n(C B) n(C B) = n(C) + n(B) – (C B) n(C B) = 27 + 42 – 60 n(C B) = 9
19.
MATHEMATICS 299 768. In
a room there are six Bengali, twelve engineers and fifteen football players. Only one of them was a Bengali Engineer who played football. Two were Bengali Engineers but did not play football and two were Bengali football players and were not engineers. If there were 24 people in the room, and at least one of them were Bengali, engineer or a football player, how many were engineers and played football but not Bengali? (GKwU K‡ÿ 6 Rb evOvwj, 12 Rb cÖ‡KŠkjx I 15 Rb dzUejvi Av‡Qb| Zv‡`i g‡a¨ †_‡K gvÎ GKRb evOvwj cÖ‡KŠkjx whwb dzUej †Lj‡Zb| `yRb wQ‡jb evOvwj cÖ‡KŠkjx hviv dzUej †Lj‡Zb bv Ges `yRb wQ‡jb evOvwj dzUejvi huviv cÖ‡KŠkjx bb| hw` H K‡ÿ †gvU 24 Rb †jvK _v‡Kb Ges Zv‡`i g‡a¨ AšÍZ GKRb evOvwj, cÖ‡KŠkjx ev dzUejvi, Z‡e Zv‡`i g‡a¨ KZRb cÖ‡KŠkjx I dzUejvi wKš‘ evOvwj bb?) [Sonali & Janata Bank (S.O. IT-2018)] a 1 b 9 c 6 d 3 d mgvavb : †gvU e¨w³i msL¨v, n(B E F) = 24 evOvwji msL¨v, n(B) = 6 cÖ‡KŠkjxi msL¨v, n(E) = 12 dzUejv‡ii msL¨v, n(F) = 15 evOvwj cÖ‡KŠkjx huviv dzUej †Lj‡Zb Zuv‡`i msL¨v, n(B E F) = 1 evOvwj cÖ‡KŠkjx wKš‘ dzUejvi bb Ggb e¨w³i msL¨v, n((B E)F) = 2 n(B E) – n (B E F) = 2 n(B E) – 1 = 2 n(B F) = 3 evOvwj dzUejvi wKš‘ cÖ‡KŠkjx bb Ggb e¨w³i msL¨v, n((B F)E) = 2 n(B F ) – n (B F E) = 2 n(B F) – 1 = 2 n(B E) = 3 cÖ‡KŠkjx I dzUejvi wKš‘ evOvwj bb Ggb e¨w³i msL¨v, = n((E F)B) = n(E F) – n(E F B) = n(E F) – 1 Avgiv Rvwb, n(B E F) = n(B) + n(E) + n(F) – n(B E) – n(E F) – n(B F) + n(B E F) 24 = 6 + 12 + 15 – 3 – n(E F) – 3 + 1 = 28 – n(E F) n(E F) = 28 – 24 = 4 cÖ‡KŠkjx I dzUejvi wKš‘ evOvwj bb Ggb e¨w³i msL¨v = n(E F) – 1 = 4 – 1 = 3 weKí mgvavb : †fbwPÎ †_‡K B(6) E(12) F(15) 6–(2+2+1) = 1 12–(2+1+x) = 9–x 15–(2+1+x) = 12–x 24 GLb, 24 = 1 + 9 – x + 12 – x + 2 + 1 + 2 + x 24 = 27 – x x = 3 769. Shonghoti and Shouhardo Clubs consist of 200 and 270 members respectively. If the total member of the two clubs is 420 then how many members belong to both clubs? (msnwZ I †mŠnv`©¨ K¬v‡ei †gvU m`m¨ msL¨v h_vµ‡g 200 I 270 Rb| hw` `ywU K¬v‡ei †gvU m`m¨ msL¨v 420 nq, Z‡e KZRb Dfq K¬v‡ei m`m¨?) [Bangladesh Bank (A.D.-2018)] a 30 b 40 c 50 d 60 c mgvavb : msnwZ K¬v‡ei m`m¨ msL¨v, N(A) = 200 †mŠnv`©¨ Ó Ó Ó , N(B) = 270 †gvU m`m¨ msL¨v N(A B) = 420 N(A B) = N(A) + N(B) – (A B) N(A B) = N(A) + N(B) – (A B) = 200 + 270 – 420 = 50 50 Rb Dfq K¬v‡ei m`m¨| 770. In a class of 78 students 41 are taking French, 22 are taking German. Of the students taking French or German, 9 are taking both courses. How many students are not enrolled in either course? (†Kv‡bv K¬v‡m 78 Rb wkÿv_x©i gv‡S 41 Rb †d«Â, 22 Rb Rvg©vb wbj| 9 Rb `ywU †Kvm©B †bB| KZRb wkÿv_x© †Kvb †Kv‡m©B AskMÖnY K‡i wbÑ) [Sonali Bank (Officer-2018)] a 6 b 15 c 24 d 33 c mgvavb : Avgiv Rvwb, N = (F G) = N(F) + N(G) – n (F G) = 41 + 22 – 9 = 54 †Kvb †Kvm©B †bq wb = 78 – 54 = 24 Rb 771. Club A has 20 members and Club B has 27. If a total of 42 people belong to the two clubs, how many people belong to both clubs? (A K¬v‡e 20 Rb m`m¨ Ges B K¬v‡e 27 Rb m`m¨ Av‡Q| hw` `yB K¬ve wgwj‡q †gvU 42 Rb m`m¨ _v‡K Zvn‡j KZRb `yB K¬v‡eB Av‡QÑ) [B.K.B. (Officer Cash-2017)] a 3 b 4 c 5 d 6 c F G (F G)
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300 PHENOM’S RECENT
BANK SOLUTION mgvavb : Avwg Rvwb, n(A B) = n(A) + n(B) – n (A B) 42 = 20 + 27 – n(A B) n(A B) = 47 – 42 = 5 772. If 61% of Bangladeshi people like coffee and 74% like tea, how many like both? (hw` 61% evsjv‡`kx gvbyl Kwd cQ›` K‡i Ges 74% Pv cQ›` K‡i| KZRb DfqwU cQ›` K‡iÑ) [B.K.B. (Officer Cash-2017)] a 13% b 16% c 26% d 35% d mgvavb : Avgiv Rvwb, n(C T) = n(C) + n(T) – n(C T) 100% = 61% + 74% – n(C T) n(C T) = 135% – 100% = 35% 35% †jvK DfqwUB cQ›` K‡i| Written 773. Among 50 people, 35 can speak English, 25 can speak both English and Bangla and each can speak at least in one of the two languages. How many of them can speak only Bangla? (50 Rb gvby‡li g‡a¨, 35 Rb Bs‡iwR, 25 Rb Bs‡iwR I evsjv Ges c‡Z¨‡K †h‡Kvb GKwU fvlv ej‡Z cv‡i| Zv‡`i g‡a¨ ïaygvÎ evsjv ej‡Z cvi‡e KZ Rb?) [Bangladesh Krishi Bank Ltd. (Officer Cash-2018)] Solution: Let, set of Bangla speaking people = B and ,, ,, English ,, ,, = E We know, n(B E) = n(B) + n(E) n(B E) 50 = n(B) + 35 25 n(B) = 40 So, 40 people can speak Bangla So, Number of people who can speak only Bangla = 40 25 = 15 774. In a survey at an airport, 55 travelers said that last year they had been to Spain, 53 to France and 79 to Germany, 18 had been to Spain and France, 17 to Spain and Germany and 25 to France and Germany, while 10 had to all three countries. How many travelers took part in the survey? (wegvbe›`‡i GKwU Rwic †`Lv hvq, 55 Rb hvÎx MZ eQi †¯ú‡b, 53 Rb d«v‡Ý Ges 79 Rb Rvg©vwb ågY K‡i‡Qb| 18 Rb †¯úb Ges d«vÝ, 17 Rb †¯úb Ges Rvg©vwb Ges 25 Rb d«vÝ Ges Rvg©vwb‡Z ågY K‡i‡Qb| 10 Rb me¸‡jv †`‡kB ågY K‡i‡Qb| KZRb Rwic AskMÖnY K‡iwQj?) [Agrani Bank Ltd. (S.O. Auditor-2018); Rupali Bank Ltd. (Officer Cash-2018)] Solution: Number of travellers who had been to spain n(s) = 55 ,, ,, ,, ,, ,, ,, ,, France n(F) = 53 ,, ,, ,, ,, ,, ,, ,, Germany n(G) = 79 ,, ,, ,, ,, ,, ,, ,, both spain and France n(S F) = 18 ,, ,, ,, ,, ,, ,, ,, both spain and Germany n(S G) = 17 ,, ,, ,, ,, ,, ,, ,, both France and Germany n(F G) = 25 ,, ,, ,, ,, ,, ,, ,, all three countries n(S F G) = 10 Total Number of travellers n(S F G) = n(S) + n(F) + n(G) n(S F) n(S G) n(F G) + n(S F G) n(S F G) = 55 + 53 + 79 18 17 25 + 10 = 137 775. 70 students are studying physics, mathematics and chemistry. 40 students study mathematics, 35 study physics and 30 study chemistry, 15 students are studying all the subjects. How many students are studying exactly two of the subjects? (70 Rb QvÎ c`v_©, MwYZ Ges imvqb GB wZbwU welq co‡Q| 40 Rb QvÎ MwYZ c‡o, 35 Rb c`v_© c‡o Ges 30 Rb imvqb c‡o| 15 Rb wZbwU welqB c‡o| KqRb `yBwU welq c‡o?) [Rupali Bank Ltd. (Officer Cash) Cancelled-2018; Sonali Bank Ltd. (Officer)-2018] A B A B Coffce (C) C T Tea (T) only English only Bangla B E Both Bangla and English [n(B E)] 50 S F G
21.
MATHEMATICS 301 Solution: From
venndiagram, Number of students studying only mathematics = 40 (x + y + 15) Number of students studying only physics = 35 (x + z + 15) Number of students studying only chemistry = 30 (y + z + 15) Total students = 70 From diagram 40 (x + y + 15) + 35 (x + z + 15) + 30 (y + z + 15) + x + y + z + 15 = 70 120 (2x + 2y + 2z + 45) + x + y + z = 70 75 – x – y – z = 70 x + y + z = 5 (Ans.) 776. Out of 85 football players, 42 have scored a goal and 54 have received a yellow card. If 5 players did not do either, what fraction of the players secored a goal and received a yellow card as well? (85 Rb dzUej †L‡jvqv‡oi gv‡S 42 Rb †Mvj K‡i‡Q Ges 54 Rb njy` KvW© †c‡q‡Q| hw` 5 Rb †KvbwUB bv K‡i Z‡e KZ Ask †L‡jvqvo †Mvj K‡i‡Q Ges njy` KvW© †c‡q‡Q?) [Sonali & Janata Bank Ltd. (SO) IT/ICT-2018] Solution: we know, n(G Y) = n(G) + n(Y) n(G Y) 85 5 = 42 + 54 n(G Y) 80 = 96 n(G Y) n(G Y) = 6 Fraction = 16 85 7. Logarithm M.C.Q 777. log 36 log 6 = [Bangladesh Bank (Officer General-2019); BangladeshBank (Officer-2018);AgraniBank (OfficerCash-2017)] a 5 b 8 c 3 d 2 d mgvavb : log 36 log 6 = log 62 log 6 = 2 log 6 log 6 ‹ logaxn = nlogax = 2 778. If logx 9 16 = 1 2 the value of the base is– (logx 9 16 = 1 2 n‡j x Gi gvbÑ) [Rupali Bank Ltd. (Officer-2019)] a 16 9 b 9 16 c 256 81 d 81 256 d mgvavb : logx 9 16 = 1 2 x 1 2 = 9 16 x = 9 16 2 = 81 256 779. If logx2 9 16 = – 1 2 the value of the base is– (logx2 9 16 = – 1 2 n‡j, jMvwi`‡gi wfwËi gvbÑ) [Combined 5 Banks (Officer-2018)] a 16 9 b 9 16 c 256 81 d 81 256 c mgvavb : GLv‡b wfwË = x2 logx2 9 16 = – 1 2 (x2 ) – 1 2 = 9 16 [ ](x2 ) – 1 2 – 2 = 9 16 – 2 [Dfqc‡ÿ – 2 NvZ wb‡q] x2 = 16 9 2 = 256 81 780. If logx 1 4 = – 2, the x = ? [Rupali Bank (Officer Cash-2018)] a –1 2 b 1 2 c 2 d 3 c mgvavb : logx 1 4 = – 2 x– 2 = 1 4 1 x2 = 1 4 x2 = 4 x = 4 x = 2 Here, x + y + z = Number of students studying exactly two subjects G n(G Y) Y 85 5 M P C x y z 15 70
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302 PHENOM’S RECENT
BANK SOLUTION 781. If x = ya , y = zb and z = xc then the value of abc is– [RupaliBank(Officer Cash-2018);AgraniBank(S.O.Auditor-2018); Bangladesh Bank (A.D.-2018); B.H.B.F.C. (S.O.-2017)] a 1 b 0 c 0.5 d infinity a mgvavb : x = ya log x = log ya = a log y a = log x log y .................. (i) y = zb log y = log zb log y = b log z b = log y log z ......................... (ii) z = xc log z = log xc = c log x c = log z log x ........................ (iii) (i) (ii) (iii) abc = log x log y log y log z log z log x abc = 1 weKí mgvavb : x = ya , y = zb , z = xc z = xc = (ya )c = yac = (zb )ac = zabc z1 = zabc abc = 1 782. If 42x + 1 = 32, then x = ? [Bangladesh Bank (A.D.-2018)] a 2 b 3 c 3 4 d 4 3 c mgvavb : 42x + 1 = 32 (22 )2x + 1 = 25 24x + 2 = 25 4x + 2 = 5 4x = 3 x = 3 4 783. If x – 7 2 = 1 128 then the value of x is– [Sonali Bank (Officer-2018)] a 8 b – 4 c 4 d 2 c mgvavb : x – 7 2 = 1 128 x 7 2 = 128 [e¨¯ÍKiY K‡i] x 7 2 = 27 x = ( )27 2 7 = 2 7 2 7 x = 22 x = 4 784. (2x–1 )2 x–5 is equal to : [Sonali Bank (Officer-2018)] a 2x2 b 4x c 4x2 d 4x3 d mgvavb : (2x–1 )2 x–5 = 22 (x–1 )2 x–5 = 22 1 x2 1 x5 = 22 1 x2 x5 = 4x3 785. Log 3 81 = ? [Agrani Bank (S.O. Auditor-2018); B.K.B. (Officer Cash-2017)] a 9 b 7 c 6 d 8 d mgvavb : log 3 81 = log 3 ( 3)8 = 8 log 3 3 = 8 1 [loga a = 1] = 8 786. If 4x + 1 = 32, then x = ? [B.K.B. (Officer Cash-2017)] a 2 b 3 c 3 2 d 2 3 c mgvavb : 4x + 1 = 32 (22 )x + 1 = 25 22x + 2 = 25 2x + 2 = 5 2x = 3 x = 3 2 787. If logx 1 9 = – 2, the x = ? [B.D.B.L. (S.O.-2017)] a – 1 3 b 1 3 c – 3 d 3 d mgvavb : logx 1 9 = – 2 x–2 = 1 9 1 x2 = 1 9 x2 = 9 x = 9 = 3 8. Inequality M.C.Q 788. If x is an integer and y = – 2x – 8, what is the least value of x for which y is less than 9? (x GKwU c~Y©msL¨v Ges y = – 2x – 8 n‡j x Gi †Kvb me©wb¤œ gv‡bi Rb¨ y Gi gvb 9 Gi Kg n‡e?) [Combined 5 Banks (Officer-2018); Sonali Bank (S.O.-2018); Bangladesh Bank (Officer General-2019); Rupali Bank Ltd. (Officer-2019)] a – 9 b – 8 c – 7 d – 6 b mgvavb : y < 9 – 2x – 8 < 9 – 2x – 8 + 8 < 9 + 8 – 2x < 17 – 2x – 2 > 17 – 2 x > – 8.5 c~Y©msL¨v wn‡m‡e x Gi me©wb¤œ gvb – 8 n‡Z n‡e|
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MATHEMATICS 303 789. If
2x – 1 – 3, then– [Bangladesh Bank (Officer General-2019)] a x – 2 b x – 2 c x – 1 d x – 1 d mgvavb : 2x – 1 – 3 2x – 1 + 1 – 3 + 1 2x – 2 2x 2 – 2 2 x – 1 790. If 1 – 2x 3, then– [Rupali Bank Ltd. (Officer-2019); Bangladesh Bank (Officer-2018), Agrani Bank (Officer Cash-2017)] a x – 2 b x – 2 c x – 1 d x – 1 d mgvavb : 1 – 2x 3 – 2x 3 – 1 – 2x 2 x – 1 [– 2 Øviv fvM K‡i] 791. The solution of the inequality | 7 – 3x | < 2 is– (| 7 – 3x | < 2 AmgZvwUi mgvavbÑ) [Combined 5 Banks (Officer-2018)] a – 3 < x < 5 3 b 3 > x > 5 3 c – 3 < x < 5 2 d – 3 < x < – 5 3 b mgvavb : | 7 – 3x | < 2 – 2 < 7 – 3x < 2 – 2 – 7 < 7 – 3x – 7 < 2 – 7 [AmgZvwUi cÖ‡Z¨K As‡k – 7 †hvM K‡i] – 9 < – 3x < – 5 9 > 3x > 5 [– 1 Øviv ¸Y Kivq AmgZvi w`K cwieZ©b] 9 3 > x > 5 3 3 > x > 5 3 792. The sum of squares of 3 consecutive integers is less than 97. What is the greatest possible value of the smallest one? (wZbwU µwgK msL¨vi e‡M©i mgwó 97 A‡cÿv †QvU| †QvU msL¨vwUi m‡e©v”P gvb KZ?) [Combined 5 Banks (Officer-2018)] a 4 b 5 c 6 d 7 a mgvavb : awi, msL¨vÎq x – 1, x, x + 1 cÖkœg‡Z, (x – 1)2 + x2 + (x + 1)2 < 97 x2 + {(x + 1)2 + (x – 1)2 } < 97 x2 + 2 (x2 + 1) < 97 3x2 + 2 < 97 3x2 < 95 x2 < 95 3 x2 < 31.66 x < 31.66 x < 25 31.66 Gi wbKUZg I ÿz`ªZi c~Y©eM© 25 x < 5 wb‡Y©q m‡e©v”P gvb 4. 793. In a graph there are two curves, y1 = 2x1 – 5 and y2 = – x2 + 10. y2 will be greater than y1 when– (GKwU †jLwP‡Î y1 = 2x1 – 5 I y2 = – x2 + 10 `ywU †iLv Av‡Q| y1 Gi Zzjbvq y2 e„nËi n‡e hw`Ñ) [Sonali & Janata Bank (S.O. IT-2018)] a x > 5 b x < 5 c – 1 < x d x < 9 b mgvavb : GKB †j‡L D‡jøwLZ GKvwaK †iLvi g‡a¨ Zzjbvi mgq ¯^vaxb PjK (x1, x2) `yB †ÿ‡Î GKB (x) n‡Z n‡e| y1 = 2x – 5 y2 = – x + 10 y2 > y1 – x + 10 > 2x – 5 – 2x – 5 < – x + 10 2x + x < 15 3x < 15 x < 5 794. In 1 – 3x 4, then– [Bangladesh Bank (A.D.-2018)] a x – 2 b x – 2 c x – 1 d x – 1 d mgvavb : 1 – 3x 4 1 – 3x – 1 4 – 1 [Dfqcÿ †_‡K 1 we‡qvM K‡i] – 3x 3 3x – 3 [– 1 Øviv ¸Y Kivq AmgZvi w`K e`j] x – 3 3 x – 1 795. The sum of 3 consecutive integers is less than 75. What is the greatest possible value of the smallest one? (3wU µwgK c~Y©msL¨vi mgwó 75 A‡cÿv Kg| ÿz`ªZg msL¨vwUi m¤¢ve¨ m‡e©v”P gvb KZ?) [Bangladesh Bank (A.D.-2018)] a 16 b 19 c 22 d 23 d mgvavb : awi, msL¨vÎq x, x + 1 I x + 2 cÖkœg‡Z, x + (x + 1) + (x + 2) < 75 3x + 3 < 75 3(x + 1) < 75 x + 1 < 75 3 x + 1 < 25 x < 25 – 1 x < 24 24 Gi Zzjbvq ÿz`ª m‡e©v”P c~Y©msL¨v = 23 wb‡Y©q m‡e©v”P gvb = 23 Written 796. Find the maximum value of z = 6x + 2y, subject to the conditions x 0, y 0, x + y = 5, x 2, y 0 [Bangladesh Bank (Officer)-2018] Solution: Given, conditions x 0 ... (i) y 0 ... (ii) x + y = 5 ... (iii) x 2 .... (iv) y 4 ... (v) Required function, zmax = 6x + 2y
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304 PHENOM’S RECENT
BANK SOLUTION From equation (i) and (iv) we get, minimum value of x is 0 and maximum value of x is 2 To get zmax we have to maximize value of x and y From equation (ii) and (v) we get, minimum value of y is 0 and maximum value of y is 4 If we take both maximum value, then x + y = 2 + 4 = 6 which does not satisfy equation .... (iii) So, to get maximum value and to satisfy equation (iii) we can use x = 1, y = 4 or x = 2, y = 3 As our function is 6x + 2y, so x must be maximzed as x is multiplied by 6 So, x = 2, y = 3 zmax = 6 2 + 2 3 = 12 + 6 = 18 797. x2 12x + 27 < 0 [Sonali & Janata Bank Ltd. (SO) IT/ICT-2018] Solution: x2 12x + 27 < 0 x2 9x 3x + 27 < 0 x(x 9) 3(x 9) < 0 (x 9) (x 3) < 0 ..... (i) sign of (x 9) sign of (x 3) sign of (x 9) (x 3) x < 3 + 3 < x < 9 + x > 9 + + + From equation (i) we can see (x 9) (x 3) < 0, that means (x 9) (x 3) has to be negative From the chart, Answer is 3 < x < 9 798. x2 13x + 40 0 [Sonali & Janata Bank Ltd. (SO) IT/ICT-2018] Solution: x2 – 13x + 40 0 x2 – 8x – 5x + 40 0 x(x 8) 5(x 8) 0 (x 5) (x 8) 0 .... (i) sign of (x 5) sign of (x 8) sign of (x 5) (x 8) x 5 + 5 < x 8 + x 8 + + + From equation (i) we can see (x 5) (x 8) 0, that means (x 5) (x 8) must be positive. From the chart, Answer is x 5 or x 8 9. Average M.C.Q 799. The average of six numbers is 14. The average of four of these numbers is 15. The average of the remaining two number is– (6wU msL¨vi Mo 14| G‡`i 4wU msL¨vi Mo 15| evwK `ywU msL¨vi Mo KZÑ) [Bangladesh Bank (Officer General-2019)] a 4 b 8 c 12 d 16 c mgvavb : 6wU msL¨vi mgwó = 14 6 ev 84 4wU ” ” = 15 4 ev 60 (–) K‡i, 2wU ” ” = 24 2wU msL¨vi Mo = 24 2 = 12 800. The average of eight numbers is 14. The average of six of these numbers is 16. The average of the remaining two numbers is– (AvUwU msL¨vi Mo 14| G‡`i g‡a¨ 6wU msL¨vi Mo 16| Aewkó `ywU msL¨vi MoÑ) [Rupali Bank Ltd. (Officer-2019); Agrani Bank (Officer Cash-2017)] a 4 b 8 c 16 d data inadequate b mgvavb : AvUwU msL¨vi mgwó = 8 14 = 112 QqwU msL¨vi mgwó = 6 16 = 96 Aewkó `ywU msL¨vi mgwó = 112 – 96 = 16 wb‡Y©q Mo = 16 2 = 8 801. Consider that w + x = – 4, x + y = 25 and y + w = 15. Then the average of w, x, y is– (w + x = – 4, x + y = 25 Ges y + w = 15 n‡j, w, x, y Gi MoÑ) [Rupali Bank (Officer Cash-2018); B.K.B. (Officer Cash-2017); B.D.B.L. (S.O.-2017)] a 3 b 4 c 5 d 6 d mgvavb : w + x = – 4 ........... (i) x + y = 25 ............ (ii) y + w = 15 .......... (iii) (i) + (ii) + (iii) (w + x) + (x + y) + (y + w) = – 4 + 25 + 15 2(w + x + y) = 36 w+ x + y = 18 Mo = w + x + y 3 = 18 3 = 6 802. The numbers 2, 3, 5 and x have an average equal to 4. What is the value of x? (2, 3, 5 Ges x Gi Mo 4 n‡j x Gi gvb?) [B.K.B. (Officer Cash-2017)] a 4 b 6 c 8 d 10 b mgvavb : 2 + 3 + 5 + x 4 = 4 2 + 3 + 5 + x = 16 x = 16 – 10 = 6
25.
MATHEMATICS 305 803. If
12a + 3b = 1 and 7b – 2a = 9, what is the average of a and b? [Sonali Bank (Officer-2018)] a 0.1 b 0.5 c 1 d 2.5 b mgvavb : †`Iqv Av‡Q, 12a + 3b = 1 ............... (i) 7b – 2a = 9 ................ (ii) a Ges b Mo = a + b 2 (i) Ges (ii) †hvM K‡i cvB, 10a + 10b = 10 a + b = 1 a + b 2 = 1 2 = 0.5 804. The average of the smallest and largest primes between 60 and 80 is– (60 †_‡K 80 Gi gv‡S e„nËg I ÿz`ªZg †gŠwjK msL¨vi MoÑ) [B.D.B.L. (S.O.-2017)] a 60 b 70 c 80 d 77 b mgvavb : 60 †_‡K 80 Gi gv‡S e„nËg †gŠwjK msL¨v = 79 Ges ÿz`ªZg †gŠwjK msL¨v 61; msL¨v `ywUi Mo = msL¨v؇qi mgwó 2 = 61 + 79 2 = 140 2 = 70 805. Which of the following is the average of first five prime numbers? (cÖ_g 5wU †gŠwjK msL¨vi MoÑ) [B.H.B.F.C. (S.O.-2017)] a 4.5 b 5.6 c 7.5 d 8.6 b mgvavb : cÖ_g 5wU †gŠwjK msL¨v 2, 3, 5, 7, 11 cuvPwU msL¨vi Mo = 2 + 3 + 5 + 7 + 11 5 = 28 5 = 5.6 806. The average of ten numbers is 7. What will be the new average if each of the numbers is multiplied by 8? (10wU msL¨vi Mo 7| hw` cÖwZ msL¨v‡K 8 Øviv ¸Y Kiv nq Z‡e bZzb MoÑ) [B.H.B.F.C. (S.O.-2017)] a 45 b 52 c 56 d 55 c mgvavb : †`Iqv Av‡Q, 10wU msL¨vi Mo 7 10wU msL¨vi mgwó = 7 10 = 70 cÖwZwU msL¨v‡K 8 Øviv ¸Y Ki‡j mgwó n‡e = 70 8 = 540 Mo n‡e = 560 10 = 56 10. Problem on Numbers M.C.Q 807. Find the largest fraction from the following : (e„nËi fMœvskwU †ei Kiæb :) [Sonali Bank (S.O.-2018)] a – 5 11 b – 8 13 c – 7 19 d – 15 97 d mgvavb : cÖwZwU fMœvs‡ki mvg‡b FYvZ¥K wPý Av‡Q| ZvB †h fMœvs‡ki mvswL¨K gvb me©wb¤œ, †mB fMœvs‡ki gvb n‡e m‡e©v”P| (a) 5 11 = 0.45 (b) 8 13 = 0.615 (c) 7 19 = 0.368 (d) 15 97 = 0.154 15 97 Gi mvswL¨K gvb me©wb¤œ – 15 97 fMœvskwU m‡e©v”P 808. The difference between two numbers is 5 and the difference between their squares is 65. What is the larger number?– (`ywU msL¨vi cv_©K¨ 5 Ges G‡`i e‡M©i cv_©K¨ 65| e„nËi msL¨vwU KZ?) [B.D.B.L. (S.O.-2017); B.H.B.F.C. (S.O.-2017); Bangladesh Bank (A.D.-2018)] a 13 b 11 c 8 d 9 d mgvavb : awi, e„nËi msL¨vwU x ÿz`ªZi msL¨vwU (x – 5) cÖkœg‡Z, x2 – (x – 5)2 = 65 x2 – [x2 – 10x + 25] = 65 10x – 25 = 65 10x = 90 x = 9 809. Find the largest fraction from the following? (wb‡Pi †Kvb fMœvskwU e„nËg) [Sonali Bank (Officer-2018)] a – 15 30 b – 8 64 c – 7 98 d – 15 90 c mgvavb : cÖwZwU fMœvs‡ki mvg‡b FYvZ¥K wPý Av‡Q| ZvB †h fMœvs‡ki mvswL¨K gvb me©wb¤œ, †mB fMœvs‡ki gvb n‡e m‡e©v”P| GLb, –15 30 = – 1 2 – 8 64 = – 1 8 – 7 98 = – 1 14 – 15 90 = – 1 6 fMœvsk¸‡jvi me¸‡jvi je 1 A_©vr ni hvi me‡P‡q eo †m fMœvskwUi mvswL¨K gvb me©wb¤œ| 1 14 Gi mvswL¨K gvb me©wb¤œ m‡e©v”P fMœvsk = – 7 98 810. If a and b are integers greater than 100 such that a + b = 300, which of the following could be the exact ratio of a to b? (hw` a Ges b, 100 Gi †P‡q eo c~Y©msL¨v Ges a + b = 300 nq Z‡e a Ges b Gi AbycvZ KZ?) [Agrani Bank (Officer Cash-2017)] a 9 to 1 b 5 to 2 c 5 to 3 d 3 to 2 d
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306 PHENOM’S RECENT
BANK SOLUTION mgvavb : †`Iqv Av‡Q, a > 100 Ges b > 100 Avevi, a + b > 300 [a Ges b c~Y©msL¨v] Option check (a) 9 : 1 300 G a = 300 9 10 = 270 b = 300 1 10 = 30 < 100 (b) 5 : 2 300 G a = 300 5 7 c~Y©msL¨v (c) 5 : 3 300 G a = 300 5 8 c~Y©msL¨v (d) 3 : 2 300 G a = 300 3 5 = 180 b = 300 2 5 = 120 811. If one number exceeds another number by 14 and the larger number is 3 2 times the smaller number, then the smaller number is– (hw` GKwU msL¨v Aci GKwU msL¨vi †P‡q 14 †ewk nq Ges e„nËi msL¨vwU ÿz`ªZi msL¨vi 3 2 ¸Y nq, Zvn‡j †QvU msL¨vwU?) [B.K.B. (Officer Cash-2017)] a 13 b 26 c 28 d 31 c mgvavb : g‡b Kwi, †QvU msL¨vwU = x eo msL¨vwU = x + 14 cÖkœg‡Z, x + 14 = 3 2 x 2x + 28 = 3x x = 28 812. The ratio of two numbers is 3 : 4 and their sum is 420. The greater one of the two numbers is– (`ywU msL¨vi AbycvZ 3 : 4 Ges msL¨v `ywUi mgwó 420| eo msL¨vwU KZ?) [B.K.B. (Officer Cash-2017)] a 360 b 240 c 180 d 120 b mgvavb : g‡b Kwi, †QvU msL¨vwU = 3x eo msL¨vwU = 4x cÖkœg‡Z, 3x + 4x = 420 7x = 420 x = 60 msL¨vwU = 4 60 = 240 Written 813. A two digit number is six times the sum of the two digits. If the digits are reversed, the number so obtained is 9 less than the original number. What is the original number? (`yB A¼ wewkó GKwU msL¨v Zvi A¼Ø‡qi †hvMd‡ji 6 ¸Y| A¼Øq ¯’vb cwieZ©b Ki‡j cÖvß msL¨v cÖK…Z msL¨vi †P‡q 9 Kg nq| cÖK…Z msL¨vwU KZ?) [Rupali Bank Ltd. (Officer-2019)] Solution: Let, unit digit is x and tenth disit is y The number is = 10y + x According to question, 10y + x = 6 (x + y) .......... (i) If the digits are reversed, the new number is 10x + y According to question, (10y + x) – (10x + y) = 9 9y – 9x = 9 y – x = 1 y = x + 1 .............. (ii) From (i) 10 (x + 1) + x = 6 (x + x + 1) 10x + 10 + x = 6(2x + 1) 11x + 10 = 12x + 6 10 – 6 = 12x – 11x x = 4 From (ii), y = 4 + 1 = 5 Original number is = 10 5 + 4 = 54 814. Find the three-digit prime number whose sum of the digits is 11 and each digit representing a prime number. Justify your answer. (wZb A‡¼i Ggb GKwU †gŠwjK msL¨v wbY©q Kiæb hvi A¼¸‡jvi mgwó 11 Ges cÖwZwU A¼B †gŠwjK msL¨v|) [Bangladesh Development Bank Ltd. (SO)-2018; Rupali Bank Ltd. (Officer Cash) Cancelled-2018] Solution: Sum of three prime is 11 possible options are, 2 + 2 + 7 = 11 3 + 3 + 5 = 11 Numbers that can be formed by 2, 2 and 7 = 227, 272, 722 Within these numbers only 227 is prime number and satisfies all the conditions of question. Now, numbers that can be formed by 3, 3 and 5 = 335, 353 and 533 within these numbers only 353 is prime number and satisfies all the conditions of question. 227 and 353 are both correct.
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MATHEMATICS 307 815. The
sum of the digits of a two-digit number is subtracted from the number. How many such two-digit numbers can be formed so that the digit in the unit place of the resulting number is 6? (`yB A‡¼i †Kv‡bv msL¨v n‡Z †mB msL¨vi A¼Ø‡qi mgwó we‡qvM Kiv nq| Ggb KZ¸‡jv msL¨v MVb Kiv m¤¢e †hb we‡qvMd‡ji GKK ¯’vbxq A¼ 6 nq?) [Bangladesh Bank (Officer)-2018] Solution: Let, Unit place of the number = Y and tenth ,, ,, ,, ,, = X Number = 10X + Y Sum of the digit = X + Y Subtracting we get = (10X + Y) (X + Y) = 9X To have 6 in the unit place value of X must be 4 as 9 4 = 36 As, x = 4 so tenth place = 4 So, possible numbers are 40, 41, 42, 43, 44, 45, 46, 47, 48, 49 So, 10 number can be formed. 816. The sum of 15 consecutive integers is 88. What is the largest of these integers? (15wU ch©vqµwgK c~Y©msL¨vi mgwó 88| c~Y©msL¨v mg~‡ni gv‡S e„nËg msL¨v †KvbwU?) [Sonali & Janata Bank Ltd. (SO) IT/ICT-2018] Solution: Let, 15 consecutive numbers are x, x + 1, x + 2, x + 3, x + 4, x + 5, x + 6, x + 7, x + 8, x + 9, x + 10, x + 11, x + 12, x + 13 and x + 14 According to question, x + x + 1 + x + 2 + x + 3 + x + 4 + x + 5 + x + 6 + x + 7 + x + 8 + x + 9 + x + 10 + x + 11 + x + 12 + x + 13 + x + 14 = 88 15x + 105 = 88 15x = 17 x = 17 15 Largest number = 17 15 + 14 = 17 + 210 15 = 193 13 which is not integer So, data in the question is not correct. 817. A two digit number is four times the sum of the two digits. If the digits are reversed, the number so obtained is 18 more than the original number. What is the original number? (`yB A‡¼i GKwU msL¨v Gi A¼Ø‡qi †hvMd‡ji 4 ¸Y| A¼ `ywU ¯’vb cwieZ©b Ki‡j cÖvß msL¨v g~j msL¨vi †P‡q 18 †ewk| g~j msL¨vwU KZ?) [Sonali Bank Ltd. (SO) IT/ICT-2018] Solution: Let, Unit digit of the number is x and tenth ,, ,, ,, ,, ,, y Number = 10y + x Sum of the digits = x + y According to question, 4(x + y) = 10y + x ... (i) If the digits are reversed, obtained number = 10x + y According to question, 10x + y = 10y + x + 18 9x = 9y + 18 x = y + 2 ... ... (ii) From (i) we get, 4(y + 2 + y) = 10y + y + 2 4(2y + 2) = 11y + 2 8y + 8 = 11y + 2 6 = 3y y = 2 From (ii), x = 2 + 2 = 4 The number = 10 2 + 4 = 24 818. Three numbers x, y and z are in A.P. and their sum is 30. Also, the sum of their squares is 308. Find the numbers. (GKwU mgvšÍi avivi wZbwU msL¨v x, y Ges z Gi mgwó 30 Ges msL¨v¸‡jvi e‡M©i mgwó 308| msL¨v wZbwU KZ?) [Bangladesh Bank (AD)-2018] Solution: According to question, Common difference of the series is y x = z y 2y = x + z ......................... (i) Again, according to question, x + y + z = 30 y + 2y = 30 [From (i)] y = 10 If, common difference = d then first number x = 10 d and second number z = 10 + d Again, x2 + y2 + z2 = 308 (10 d)2 + 102 + (10 + d)2 = 308 100 20d + d2 + 100 + 100 + 20d + d2 = 308 2d2 + 300 = 308 d2 = 4 d = 2 If d = 2, x = 10 2 = 8 z = 10 + 2 = 12 If d = 2 x = 10 (2) = 12 z = 10 + (2) = 8 So, Three numbers are 8, 10, 12 11. Problem on Ages M.C.Q 819. The present age of Habib and Shikhan are in the ratio of 6 : 4. Five years ago their ages were in the ratio of 5 : 3. How old is Habib now? (nvwee I wkL‡bi eZ©gvb eq‡mi AbycvZ 6 : 4| cuvP eQi c~‡e© Zv‡`i eq‡mi AbycvZ wQj 5 : 3| nvwe‡ei eZ©gvb eqm KZ?) [Rupali Bank (Officer Cash-2018); B.K.B. (Officer Cash-2017); B.D.B.L. (S.O.-2017)] a 24 b 30 c 36 d 42 b
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308 PHENOM’S RECENT
BANK SOLUTION mgvavb : nvwee I wkL‡bi eZ©gvb eq‡mi AbycvZ = 6 : 4 = 3 : 2 awi, nvwe‡ei eZ©gvb eqm = 3x wkL‡bi Ó Ó = 2x 5 eQi c~‡e© Zv‡`i eq‡mi AbycvZ wQj (3x – 5) : (2x – 5) cÖkœg‡Z, (3x – 5) : (2x – 5) = 5 : 3 3x – 5 2x – 5 = 5 3 10x – 25 = 9x – 15 x = 10 nvwe‡ei eZ©gvb eqm = 3 10 = 30 eQi 820. Today is Aziz’s 12th birthday and his father’s 40th birthday. How many years from today will Aziz’s father be twice as old as Aziz’s at that time? (AvR‡K AvwR‡Ri 12 Zg Rb¥w`b Ges Zvi wcZvi 40 Zg Rb¥w`b| GLb †_‡K KZ eQi ci AvwR‡Ri wcZvi eqm AvwR‡Ri eq‡mi wظY n‡e?) [Agrani Bank (S.O. Auditor-2018); B.K.B. (Officer Cash-2017); B.D.B.L. (S.O.-2017)] a 12 b 24 c 18 d 16 d mgvavb : g‡b Kwi, x eQi ci AvwR‡Ri wcZvi eqm, AvwR‡Ri eq‡mi wظY n‡e| cÖkœg‡Z, 2(12 + x) = 40 + x 24 + 2x = 40 + x x = 16 821. Mira is 30 times older than her son. 18 years later she will be thrice as old as her son. What is Mira’s present age? (wgivi eqm Zvi †Q‡ji 30 ¸Y| 18 eQi ci wgivi eqm Zvi †Q‡ji eq‡mi wZb¸Y n‡e| wgivi eZ©gvb eqmÑ) [Agrani Bank (Officer Cash-2017)] a 36 b 40 c 52 d 86 b mgvavb : g‡b Kwi, eZ©gv‡b wgivi †Q‡ji eqm = x eQi eZ©gv‡b wgivi eqm = 30x eQi 18 eQi ci †Q‡ji eqm = (x + 18) eQi 18 ,, ,, wgivi ,, = (30x + 18) eQi cÖkœg‡Z, 30x + 18 = 3(x + 18) 30x + 18 = 3x + 54 27x = 36 x = 4 3 wgivi eZ©gvb eqm = 30 4 3 = 40 eQi 822. If a man was r years old s years ago, how many years old will he be t years from now? (hw` GKRb e¨w³i eqm s eQi Av‡M r wQj, Zvn‡j t eQi c‡i Zvi eqm KZ n‡eÑ) [B.H.B.F.C. (S.O.-2017)] a s + r + t b rs + t c s – r + t d r – s + t a mgvavb : s eQi Av‡M e¨w³wUi eqm wQj r eQi e¨w³wUi eZ©gvb eqm (r + s) eQi GLb †_‡K t eQi ci e¨w³i eqm (r + s + t) eQi 823. Samir is twice as old as Babul was two years ago. If the difference between their ages is 2 years, how old is Samir now? (evey‡ji `yB eQi Av‡Mi eq‡mi wظY mvwg‡ii eZ©gvb eqm| hw` Zv‡`i eq‡mi cv_©K¨ 2 eQi nq, Zvn‡j mvwg‡ii eqmÑ) [B.H.B.F.C. (S.O.-2017)] a 8 years b 6 years c 10 years d 12 years a mgvavb : g‡b Kwi, evey‡ji `yB eQi Av‡Mi eqm = x eQi mvwg‡ii eZ©gvb eqm = 2x eQi evey‡ji eZ©gvb eqm = x + 2 eQi Avevi, 2x – (x + 2) = 2 x – 2 = 2 x = 4 mvwg‡ii eZ©gvb eqm = 2 4 = 8 eQi Written 824. Shakib is twice as old as Fahim. Four years ago, Shakib was six years younger than three times of Fahims age at that time. How old will they be in two years from now? (mvwK‡ei eqm dvwn‡gi eq‡mi wظY| Pvi eQi Av‡M, mvwK‡ei eqm dvwn‡gi eq‡mi 3 ¸Y A‡cÿv 6 eQi Kg wQj| 2 eQi ci Zv‡`i eqm KZ n‡e?) [Sonali & Janata Bank Ltd. (SO) IT/ICT-2018] Solution: Let, Fahim's age is x years Shakib's age is 2x years 4 years age, Fahim's age was (x 4) and Shakib's age was (2x 4) According to question, 3(x 4) 6 = 2x 4 3x 12 6 = 2x 4 x = 14 So, after 2 years Fahim's age will be = 14 + 2 = 16 years and shakib's age will be = 2 14 + 2 = 30 years 12. Percentage M.C.Q 825. Bus fares were recently increased from Taka 1.70 to Taka 2.00. What was the approximate percentage of increase? (m¤úªwZ evm fvov 1.7 UvKv †_‡K 2 UvKv Kiv n‡q‡Q| kZKiv e„w×?) [Bangladesh Bank (Officer General-2019)] a 18% b 15% c 0.15% d 0.18% a mgvavb : kZKiv e„w× = †gvU fvov e„w× Avw` fvov 100% = 2 – 1.70 1.70 100% = 0.3 1.7 100% > 18%
29.
MATHEMATICS 309 826. Which
of the numbers below is not equivalent to 20%? (wb‡Pi †KvbwU 20% Gi mgZzj¨ bq?) [Bangladesh Bank (Officer General-2019)] a 1 5 b 20 100 c 0.5 d 0.2 c mgvavb : 20% = 20 100 = 1 5 = 0.2 mwVK DËi: 0.5| 827. Every 3 minutes, 4 litres of water are poured into a 2000 litre tank, After 2 hours, what percent of the tank will be full? (GKwU 2000 wjUvi U¨v‡¼ cÖwZ 3 wgwb‡U 4 wjUvi cvwb Xvjv nq| 2 N›Uv ci U¨v‡¼i kZKiv KZ Ask fwZ© nq?) [Bangladesh Bank (Officer General-2019); Rupali Bank Ltd. (Officer-2019)] a 0.4% b 4% c 8% d 12% c mgvavb : 2 N›Uv = 2 60 ev 120 wgwbU 3 wgwb‡U Xvjv nq 4 wjUvi 120 ” ” ” 4 3 120 ” = 160 wjUvi U¨v¼wU c~Y© nq kZKiv = 160 2000 100% = 8% 828. If w is 10% less than x, and y is 30% less than z, then wy is what percent less than xz? (W Gi gvb x Gi gvb A‡cÿv x Gi 10% cwigvY Kg Ges y Gi gvb z Gi gvb A‡cÿv z Gi 30% cwigvY Kg| Zvn‡j wy Gi gvb xz Gi gvb A‡cÿv xz Gi KZ kZvsk Kg?) [RupaliBankLtd.(Officer-2019);SonaliBank(S.O.-2018)] a 10% b 20% c 37% d 40% c mgvavb : w = x – x Gi 10% w = x – 10 100 x w = 9 10 x y = z – z Gi 30% y = z – 30 100 z y = 7 10 z wy = 9 10 x 7 10 z wy = 63 100 z wy = 100 – 37 100 z wy = 1 – 37 100 z wy = z – 37 100 z wy = z – z Gi 37% 829. If 10% of x is equal to 25% of y, and y = 16, what is the value of x? (hw` x Gi 10% Gi gvb y Gi 25% Gi mgvb nq Ges y = 16 nq, Z‡e x Gi gvb KZ?) [Combined 5 Banks (Officer-2018)] a 4 b 6.4 c 24 d 40 d mgvavb : x Gi 10% = 10 100 x = x 10 y Gi 25% = 25 100 y = y 4 cÖkœg‡Z, x 10 = y 4 x = 10 4 y x = 5 2 y x = 5 2 16 x = 40 830. Which of the numbers below is not equivalent to 4%? (wb‡Pi †Kvb msL¨vwU 4% Gi mgZzj¨ bq?) [Sonali Bank (S.O.-2018)] a 1 25 b 4 100 c 0.40 d 0.04 c mgvavb : 4% = 4 100 = 1 25 Avevi, 4% = 4 100 = 1 10 4 10 = 1 10 0.4 = 0.04 4% 0.40 mwVK DËi : C weKí mgvavb : Ackb¸‡jv †PK K‡i †`Lv hvq : (a) 1 25 = 1 25 100% = 4% (b) 4 100 = 4 100 100% = 4% (c) 0.40 = 0.40 100% = 40% (d) 0.04 = 0.04 100% = 4% mwVK DËi : C 831. What is the original price of a T-shirt, if the sale price after 15% discount is 272? (15% g~j¨ Qv‡o †Kv‡bv wU-kvU© Gi weµqg~j¨ 272 n‡j cÖK…Z g~j¨ KZ?) [Rupali Bank (Officer Cash-2018); B.D.B.L. (S.O.-2017)] a 300 b 280 c 320 d 314 c mgvavb : 15% g~j¨Qvo Gi A_© n‡jv : cÖK…Z g~j¨ 100 UvKv n‡j weµqg~j¨ (100 – 15) = 85 UvKv weµqg~j¨ 85 UvKv n‡j cÖK…Zg~j¨ 100 UvKv Ó 1 Ó Ó Ó 100 85 Ó Ó 272 Ó Ó Ó 100 85 272 Ó = 320 UvKv 832. If x is 30% greater than y, what percent of y is x? (x hw` y Gi Zzjbvq 30% eo nq, Z‡e x, y Gi KZ kZvsk?) [Agrani Bank (S.O. Auditor-2018); Rupali Bank (Officer Cash-2018)] a 70 b 77 c 120 d 130 d
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310 PHENOM’S RECENT
BANK SOLUTION mgvavb : x = y + y Gi 30% x = y + 30 100 y x = y + 3 10 y x = 13 10 y x y = 13 10 = 13 10 100% = 130% 833. As the price of mango has reduced 20%, it is now possible to buy 2 more mangoes at Tk. 12. What is the current price of 50 mangoes? (Av‡gi `vg 20% K‡g †M‡j, GLb 12 UvKvq 2wU †ewk Avg cvIqv hvq| 50wU Av‡gi eZ©gvb g~j¨?) [Sonali Bank (Officer-2018)] a Tk. 50 b Tk. 40 c Tk. 30 d Tk. 60 d mgvavb : g‡b Kwi, c~‡e© 100 UvKvq cvIqv †hZ xwU Avg eZ©gvb xwU Avg cvIqv hvq (100 – 20) ev 80 UvKvq cÖwZwU Av‡gi c~e©g~j¨ = 100 x UvKv Ges ,, ,, eZ©gvb g~j¨ = 80 x UvKv c~‡e©, 100 x UvKvq cvIqv †hZ 1wU Avg 12 ,, ,, ,, 12x 100 ,, ,, eZ©gv‡b, 80 x UvKvq cvIqv hvq 1wU Avg 12 ,, ,, ,, 12x 80 ,, ,, cÖkœg‡Z, 12x 80 – 12x 100 = 2 60x – 48x 400 = 2 12x = 800 x = 200 3 200 3 wU Av‡gi eZ©gvb g~j¨ 80 UvKv 1wU ,, ,, ,, 80 3 200 UvKv 50wU ,, ,, ,, 80 3 50 200 UvKv = 60 UvKv 834. If the salary of an employee is reduced by 10 percent for his late attendance and then increased by 10 percent on a pardon, how much does he lose? (hw` †Kvb Kg©Pvixi †eZb 10% K‡g hvq †`wi K‡i Awd‡m Avmvi Rb¨ Ges c‡i 10% e„w× Kiv nq ÿgv PvIqvi Rb¨, Zvn‡j Zvi †eZb kZKiv KZUzKz n«vm †cj) [Sonali Bank (Officer-2018)] a 2% b 1% c – 1 2 % d 9% b mgvavb : awi, Kg©Pvixi eZ©gvb †eZb = 100 UvKv cÖ_‡g 10% K‡g †M‡j †eZb = 100 – 10 = 90 UvKv Avevi, 10% evo‡j †eZb = 90 + 90 Gi 10% = 90 + 90 10 100 = 99 UvKv 100 UvKvq †eZb K‡g = (100 – 99) = 1 UvKv kZKiv 1% n«vm †cj weKí mgvavb : kZKiv n«vm = 10 – 10 – 10 10 100 = – 1% 1% n«vm cvq| 835. 35% of Nabila’s income is equal to 25% of Nuru’s income. The ratio of their income is– (bvwejvi 35% Avq byiæi 25% Av‡qi mgvb| Zv‡`i Av‡qi AbycvZÑ) [Sonali Bank (Officer-2018)] a 5 : 7 b 4 : 7 c 7 : 3 d 4 : 3 a mgvavb : awi, bvwejvi Avq x UvKv Ges byiæi Avq y UvKv cÖkœg‡Z, x Gi 35% = y Gi 25% x 35 100 = y 25 100 x y = 25 100 100 35 x y = 5 7 x : y = 5 : 7 836. If the length of a rectangle is increased by 20% and width is decreased by 20% what is the change in area of the rectangle? (hw` AvqZ‡ÿ‡Îi ˆ`N©¨ 20% e„w× Kiv nq Ges cÖ¯’ 20% Kgv‡bv nq Zvn‡j AvqZ‡ÿ‡Îi †ÿÎd‡ji kZKiv wK cwieZ©b n‡e?) [Agrani Bank (Officer Cash-2017)] a Unchanged b decreases by 4% c increases by 4% d increases by 5% b mgvavb : g‡b Kwi, AvqZ‡ÿ‡Îi ˆ`N©¨ x GKK Ges ,, cÖ¯’ y GKK AvqZ‡ÿ‡Îi †ÿÎdj = xy eM© GKK ˆ`N©¨ 20% evov‡bv n‡j, bZzb ˆ`N©¨ = x + x Gi 20% = 1.2x cÖ¯’ 20% Kg‡j, bZzb cÖ¯’ = y – y Gi 20% = .8y bZzb †ÿÎdj = 1.2x .8y = 0.96 xy cwiewZ©Z †ÿÎdj = xy – 0.96 xy = 0.04 xy †ÿÎd‡ji kZKiv cwieZ©b = 0.04xy xy 100% = 4% †ÿÎdj 4% n«vm cv‡e|
31.
MATHEMATICS 311 weKí mgvavb: †ÿÎdj
cwieZ©‡bi nvi = 20 + (–20) + 20 (–20) 100 % = 20 – 20 – 400 100 % = – 4% †ÿÎdj 4% n«vm cvq| 837. What is the original price of a T-shirt, if the sale price after 16% discount is 264? (16% Qv‡o wU kv‡U©i g~j¨ 264 UvKv n‡j, wU kv‡U©i cÖK…Z g~j¨ KZ?) [B.K.B. (Officer Cash-2017)] a 300 b 214 c 320 d 314 d mgvavb : kv‡U©i cÖK…Z g~j¨ x n‡j, 16% Qv‡o weµq g~j¨ x – x Gi 16% = x – x 16 100 = 84x 100 = 21x 25 cÖkœg‡Z, 21x 25 = 264 x = 264 25 21 = 314.28 314 UvKv 838. If y% of x = 29, then x = ? [B.K.B. (Officer Cash-2017)] a 2900 y b 29x y c 29y x d 29xy a mgvavb : x Gi y% = 29 x y 100 = 29 x = 2900 y 839. If A’s income is 25%less than that of B, then what percent is B’s income more than that of A? (hw` A Gi Avq B Gi †P‡q 25% Kg nq Zvn‡j B Gi Avq A Gi †_‡K kZKiv KZ †ewk?) [B.K.B. (Officer Cash-2017)] a 33.33 b 66.67 c 11.67 d 31.50 a mgvavb : awi, B Gi Avq = 100 UvKv A Gi Avq = (100 – 25) UvKv = 75 UvKv B Gi Avq †ewk = (100 – 75) = 25 UvKv A Gi Avq 75 UvKv n‡j B Gi †ewk 25 UvKv A ,, ,, 100 ,, ,, B ,, ,, 25 75 100 ,, = 33.33 UvKv 840. After a 20% price decrease, a computer monitor is on sale for Tk. 7200. What is its orginal price? (20% g~j¨ n«v‡m GKwU Kw¤úDUvi gwbUi 7200 UvKvq wewµ Kiv nq| cÖK…Z g~j¨ KZ?) [B.K.B. (Officer Cash-2017)] a Tk. 9000 b Tk. 10000 c Tk. 11000 d Tk. 12000 a mgvavb : g‡b Kwi, gwbU‡ii cÖK…Z g~j¨ = x UvKv cÖkœg‡Z, x – x Gi 20% = 7200 x – x 20 100 = 7200 4x 5 = 7200 4x = 5 7200 x = 5 7200 4 = 9000 841. A cricket team has won 40 games out of 60 played. It has 32 more games to play. How many of these must the team win to make it record 70% win for the season? (GKwU wµ‡KU wUg 60wU g¨v‡P 40wU‡Z wR‡Z‡Q| wUg‡K AviI 32wU g¨vP †Lj‡Z n‡e| Avi KZ g¨vP wRZ‡j GB wmR‡b 70% R‡qi †iKW© _vK‡e?) [B.D.B.L. (S.O.-2017)] a 20 b 25 c 23 d 32 b mgvavb : †gvU g¨vP = 60 + 32 = 92wU 70% R‡qi †iKW© ivL‡Z, †gvU g¨vP wRZ‡Z n‡e = 92 Gi 70% = 92 70 100 = 64.4wU g¨vP wR‡Z‡Q 40wU AviI wRZ‡Z n‡e = 64.4 – 40 = 24.4 > 25wU 842. Three workers X, Y and Z are paid a total of Tk. 5,500 for a particular job. X is paid 133.33% of the amount paid to Y and Y is paid 75% of amount paid to Z. How much is paid to Z? (wZbRb kÖwgK x, y Ges z †K GKwU wbw`©ó Kv‡Ri Rb¨ 5500 UvKv †`Iqv nq| x †K y Gi 133.33% Ges y †K z Gi 75% †`Iqv nq| z †K KZ UvKv †`Iqv nq?) [B.D.B.L. (S.O.-2017)] a Tk. 1780 b Tk. 1890 c Tk. 1975 d Tk. 2000 d mgvavb : cÖkœg‡Z, x = y Gi 133.33% = y 133.33 100 x = 1.33y ... ... (i) y = z Gi 75% = z 75 100 y = 3z 4
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312 PHENOM’S RECENT
BANK SOLUTION y Gi gvb (i) G ewm‡q cvB, x = 1.33 3z 4 = 0.9975 z cÖkœg‡Z, x + y + z = 5500 0.9975 z + 3z 4 + z = 5500 2.7475 z = 5500 z = 5500 2.7475 = 5500 2.75 = 2000 UvKv Written 843. A teacher has 6 hours to grade all the papers submitted by the 35 students in his class. He gets through the first 5 papers in 1 hour. How much faster should he work to grade the remaining papers in the allotted time? (GKRb wkÿ‡Ki 35 Rb wkÿv_©xi LvZv †MÖwWs Kivi Rb¨ 6 NÈv mgq †`Iqv nj| cÖ_g 5wU LvZv †MÖwWs Ki‡Z 1 NÈv mgq jv‡M| KZ `ªæZ LvZv †MÖwWs Ki‡j wbw`©ó mg‡q †kl Ki‡Z cvi‡eÑ) [Rupali Bank Ltd. (Officer-2019)] Solution: Time left = (6 – 1) or 5 hours Papers left for grading = (35 – 5) or 30 papers Now, the teacher has to grade 30 5 or 6 papers per hour The teacher has to be 6 – 5 5 100% faster = 20% faster 844. A man’s salary in 2015 was Tk. 20,000 per annum and it increased by 10% each year. Find how much he earned in the years 2015 to 2017 inclusive. (2015 mv‡j GK e¨w³i evwl©K Avq wQj 20000 Tk Ges cÖwZ eQi †eZb 10% K‡i e„w× cvq| 2015 mvj †_‡K 2017 mvj ch©šÍ H e¨w³i †gvU Avq KZ?) [Agrani Bank Ltd. (Officer Cash-2018); Rupali Bank Ltd. (Officer Cash) Cancelled-2018] Solution: In 2015, Man's annual salary = 20000 Tk In 2016, annual salary = 20000 + 20000 10 100 = 22000 Tk In 2017, annual salary = 22000 + 22000 10 100 = 24200 Tk So, From 2015 to 2017, Total earnings = 20000 + 22000 + 24200 = 66200 Tk (Ans.) 845. A shopkeeper sells two shirts at the same price. He makes 10% profit on one and loses 10% on the other. How much in percentage does he gain or lose? (GKRb †`vKvb`vi `ywU kvU© GKB `v‡g wewµ K‡i| GKwU‡Z 10% jvf K‡i Ges Ab¨wU‡Z 10% ÿwZ nq| †gv‡Ui Dci kZKiv KZ jvf ev ÿwZ nq?) [Agrani Bank Ltd. (S.O. Auditor-2018); Rupali Bank Ltd. (Officer Cash-2018)] Solution: Shopkeeper sells two shirts in same price. for 10% profit he sells 1st shirt = (100 + 10) Tk sell again for 10% loss he sells 2nd shirt = (110 110 of 10%) = (110 11) Tk = 99 Tk. Loss percentage = cost price selling price cost price 10% = 100 99 100 100% = 1 100 100% = 1% 846. The price of a shirt and a pant together is Tk. 1,300. If the price of the shirt increases by 5% and that of the pant by 10%, it costs Tk. 1,405 to buy those two things. Find the respective price of a shirt and a pant. (GKwU kvU© Ges GKwU c¨v‡›Ui g~j¨ GK‡Î 1300 UvKv| hw` kv‡U©i g~j¨ 5% e„w× cvq Ges c¨v‡Èi g~j¨ 10% e„w× cvq Z‡e kvU© I c¨v‡›Ui g~j¨ nq 1405 UvKv| Z‡e kvU© I c¨v‡›Ui g~j¨ KZ?) [Bangladesh House Building Finance Corporation (SO) Written-2017] Solution: Let, price of the shirt = x Tk So, ,, ,, ,, pant = (1300 x) Tk If price of shirt increases by 5% then price of shirt = x + 5% of x = x + x 5 100 = 21x 20 If price of pant increases by 10% The price of pant = (1300 x) + 10% of (1300 x) = 1300 x + 1300 x 10 = 13000 10x + 1300 x 10 = 14300 11x 10
33.
MATHEMATICS 313 According to
question, 21x 20 + 14300 11x 10 = 1405 21x + 28600 22x 20 = 1405 x + 28600 = 28100 28600 28100 = x x = 500 Price of shirt = 500 Tk and ,, ,, pant = 1300 500 = 800 Tk 847. A customer bought 5 pencils and 6 erasers at Tk. 80. Next week, the price of each pencil increases by 20%, but the price of erasers remains unchanged. Now, the customer buys 2 pencils and 3 erasers at Tk. 39. Find the new price of each pencil.? (GKRb †µZv 80 UvKv w`‡q 5wU †cwÝj Ges 6wU B‡iRvi wKbj| c‡ii mßv‡n cÖwZwU †cw݇ji g~j¨ 20% †e‡o hvq, wKš‘ B‡iRv‡ii g~j¨ cwieZ©b nq bv| Ggb †µZv 2Uv †cwÝj Ges 3Uv B‡iRvi 39 UvKvq wK‡b| cÖwZwU †cw݇ji bZzb g~j¨ KZ?) [Bangladesh House Building Finance Corporation (SO) Written-2017] Solution: Let, previous price of each pencil was x Tk and ,, ,, ,, ,, eraser ,, y Tk According to the question, 5x + 6y = 80 ... (i) Next week after 20% increment, new price of the pencil = x + 20% of x = x + x 20 100 = 6x 5 Price of eraser doesn’t change Now, According to the question, 2 6x 5 + 3y = 39 12x 5 + 3y = 39 ... (ii) (i) (ii) 2 5x + 6y = 80 24x 5 + 6y = 78 () () () 5x 24x 5 = 2 x 5 = 2 x = 10 New price of pencil = 6 10 5 = 12 (Ans.) 13. Ratio and Proportion M.C.Q 848. If x : y = 5 : 3, then (8x – 5y) : (8x + 5y) = ? [Bangladesh Bank (Officer General-2019); Sonali Bank (S.O.- 2018); Agrani Bank (Officer Cash-2017)] a 5 : 11 b 6 : 5 c 5 : 6 d 3 : 8 a mgvavb : †`Iqv Av‡Q, x : y = 5 : 3 x y = 5 3 x y 8 5 = 5 3 8 5 8x 5y = 8 3 8x – 5y 8x + 5y = 8 – 3 8 + 3 = 5 11 (8x – 5y) : (8x + 5y) = 5 : 11 849. Two numbers are in the ratio 2 : 5. If 16 is added to both the numbers, their ratio becomes 1 : 2. The numbers are– (`ywU msL¨vi AbycvZ 2 : 5| Df‡qi mv‡_ 16 †hvM Ki‡j G‡`i AbycvZ nq 1 : 2| msL¨vØqÑ) [Rupali Bank Ltd. (Officer-2019)] a 16, 40 b 20, 50 c 28, 70 d 32, 80 d mgvavb : awi, msL¨vØq 2x I 5x cÖkœg‡Z, 2x + 16 5x + 16 = 1 2 5x + 16 = 4x + 32 x = 16 msL¨vØq 2 16 = 32 I 5 16 = 80 850. If x : y = 5 : 3, then (8x + 5y) : (8x – 5y) = ? (hw` x : y = 5 : 3 nq, Z‡e (8x + 5y) : (8x – 5y) = ?) [Combined 5 Banks (Officer-2018)] a 5 : 11 b 6 : 5 c 5 : 6 d 11 : 5 d mgvavb : x : y = 5 : 3 x y = 5 3 8 5 x y = 8 5 5 3 ; [Dfqcÿ‡K 8 5 Øviv ¸Y K‡i] 8x 5y = 8 3 8x + 5y 8x – 5y = 8 + 3 8 – 3 ; [†hvRb-we‡qvRb K‡i] 8x + 5y 8x – 5y = 11 5 (8x + 5y) : (8x – 5y) = 11 : 5