Q.1 100 cards are numbered from 1 to 100. The probabilitythat the randomlychosen card has a digit 5 is:
(A) 0.01 (B) 0.09 (C) 0.19 (D) 0.18
Q.2 A quadratic equation is chosen from the set of all the quadratic equations which are unchanged by
squaringtheir roots.The chance that thechosen equation has equal roots is :
(A) 1/2 (B) 1/3 (C) 1/4 (D) 2/3
Q.3 If the letters of the word "MISSISSIPPI" are written down at random in a row, the probability that no
two S's occur together is :
(A) 1/3 (B) 7/33 (C) 6/13 (D) 5/7
Q.4 A sample space consists of 3 samplepoints with associated probabilities given as 2p, p2, 4p – 1 then
(A) p = 3
11  (B) 3
10  (C)
4
1
< p <
2
1
(D) none
Q.5 Acommitteeof5is tobechosenfrom agroupof9 people.Theprobabilitythat acertain married couple
will either servetogetheror not atall is :
(A) 1/2 (B) 5/9 (C) 4/9 (D) 2/3
Q.6 There are onlytwo women among20persons taking part inapleasure trip. The 20 persons aredivided
into twogroups,each group consistingof10 persons. Then theprobabilitythat the twowomenwill be
in thesamegroupis :
(A) 9/19 (B) 9/38 (C) 9/35 (D) none
Q.7 A bagcontain 5 white, 7 black, and 4 red balls, find the chance that three balls drawn at random are all
white.
Q.8 If four coins are tossed, find the chance that there should be two heads and two tails.
Q.9 Thirteen persons take their places at a round table, show that it is five to one against two particular
persons sittingtogether.
Q.10 Inshufflingapackofcards, fourareaccidentallydropped, findthechancethat themissingcards should
be one from each suit.
Q.11 Ahas3shares inalotterycontaining3prizesand9blanks,Bhas2sharesinalotterycontaining2 prizes
and 6 blanks. Compare their chances of success.
Q.12 Therearethreeworks,oneconsistingof3volumes,oneof4andtheotherofone volume.Theyareplaced
onashelfatrandom,provethat thechancethatvolumesofthesameworksare alltogetheris
140
3
.
Q.13 The letter forming the word Clifton are placed at random in a row. What is the chance that the two
vowels cometogether?
CLASS : XII (ABCD) DPP ON PROBABILITY DPP. NO.- 1

Q.14 Three bolts and three nuts are put in a box. If two parts arechosen at random, find the probabilitythat
one is a bolt and one is a nut.
Q.15 There are 'm' rupees and 'n' ten nP's, placed at random in a line. Find the chance of the extreme coins
beingbothten nP's.
Q.16 A fairdie is tossed. Ifthe numberis odd,find the probabilitythat it is prime.
Q.17 Three fair coins are tossed. If both heads and tails appear, determine the probabilitythat exactly one
head appears.
Q.18 3 boysand 3girls sitin arow. Findtheprobabilitythat (i)the3 girls sit together. (ii)theboysare girls sit
inalternativeseats.
Q.19 A coin is biased so that heads is three times as likelyto appear as tails. Find P (H) and P (T).
Q.20 In a handat "whist" what is the chance that the 4 kings are held bya specified player?

CLASS : XII (ABCD) DPP ON PROBABILITY DPP. NO.- 2
After 2nd Lecture
Q.1 Given two independent eventsA, B such that P(A) = 0.3, P(B) = 0.6. Determine
(i) P (A and B) (ii) P (A and not B) (iii) P(notAand B)
(iv) P(neitherAnor B) (v) P (A or B)
Q.2 Acardisdrawnat randomfromawellshuffleddeck ofcards. Findtheprobabilitythatthecardis a
(i) king or a red card (ii)cluboradiamond (iii)kingoraqueen
(iv) kingor an ace (v) spade or a club (vi) neither aheart nor a king.
Q.3 A coin is tossed and a die is thrown. Find the probabilitythat the outcome will be a head or a number
greater than 4.
Q.4 LetAand B be events such that )
A
(
P
~
= 4/5, P(B) = 1/3, P(A/B) = 1/6, then
(a) P(A  B) ; (b) P(A  B) ; (c) P(B/A) ; (d) Are A and B independent?
Q.5 IfAand B are two events such that P (A) =
4
1
, P (B) =
2
1
and P (Aand B) =
8
1
, find
(i) P (A or B), (ii) P(notAand not B)
Q.6 A5digitnumberisformedbyusingthedigits0,1,2,3,4 &5withoutrepetition.Theprobabilitythatthe
numberisdivisibleby6is:
(A) 8 % (B) 17 % (C) 18 % (D) 36 %
Q.7 An experiment results in four possible out comes S1, S2, S3 & S4 with probabilities p1, p2, p3 & p4
respectively.Whichoneofthefollowingprobabilityassignment ispossbile.
[Assume S1 S2 S3 S4 aremutuallyexclusive]
(A) p1 = 0.25 , p2 = 0.35 , p3 = 0.10 , p4 = 0.05
(B) p1 = 0.40 , p2 =  0.20 , p3 = 0.60 , p4 = 0.20
(C) p1 = 0.30 , p2 = 0.60 , p3 = 0.10 , p4 = 0.10
(D) p1 = 0.20 , p2 = 0.30 , p3 = 0.40 , p4 = 0.10
Q.8 In throwing3 dice, the probabilitythat atleast 2 ofthe three numbers obtained are same is
(A) 1/2 (B) 1/3 (C) 4/9 (D) none
Q.9 Thereare4defectiveitemsinalot consistingof10items.Fromthis lotweselect 5itemsat random. The
probabilitythat therewillbe2defectiveitemsamongthem is
(A)
2
1
(B)
5
2
(C)
21
5
(D)
21
10
Q.10 From a pack of 52 playingcards, face cards and tens are removed and kept aside then a card is drawn
at random fromthe ramainingcards.If
A : The event that the card drawn is an ace
H : The event that the card drawn is a heart
S : The event that the card drawn is a spade
thenwhichofthefollowingholds?
(A) 9 P(A) = 4 P(H) (B) P(S) = 4P (A  H)
(C) 3 P(H) = 4 P(A S) (D) P(H) = 12 P(A S)

Q.11 6marriedcouples arestandinginaroom. If4peoplearechosenatrandom, then thechancethat exactly
one marriedcouple is amongthe4 is :
(A)
16
33
(B)
8
33
(C)
17
33
(D)
24
33
Q.12 The chance that a 13 card combinationfrom a pack of52 playing cards is dealt to a player in a game of
bridge, in which 9 cards are of the same suit, is
(A)
13
52
4
39
9
13
C
C
·
C
·
4
(B)
13
52
4
39
9
13
C
C
·
C
·
!
4
(C)
13
52
4
39
9
13
C
C
·
C
(D) none
Q.13 If two of the 64 squares are chosen at random ona chess board, the probabilitythat theyhave a side in
commonis:
(A) 1/9 (B) 1/18 (C) 2/7 (D) none
Q.14 Two red counters, three green counters and 4 blue counters are placed in a row in random order. The
probabilitythat no twoblue counters are adjacent is
(A)
99
7
(B)
198
7
(C)
42
5
(D) none
Q.15 Theprobabilitiesthat astudentwillreceiveA,B,CorDgradeare0.40, 0.35,0.15 and0.10respectively.
Findtheprobabilitythat astudentwill receive
(i) not anAgrade (ii) B or C grade (iii) at most C grade
Q.16 Inasinglethrowofthreedice, determinethe probabilityofgetting
(i) a total of 5 (ii) a total of at most 5 (iii) a total of at least 5.
Q.17 A dieis thrownonce. IfE is the event "the numberappearing is a multiple of 3" and F is theevent "the
numberappearingiseven",findtheprobabilityoftheevent"EandF".AretheeventsEandFindependent?
Q.18 Inthetwodiceexperiment, ifEistheeventofgettingthe sumofnumberondiceas11 and Fis theevent
of gettinga number other than 5 on the first die, find P(E and F).AreE and F independent events?
Q.19 Anatural numberx is randomlyselectedfrom theset offirst 100 naturalnumbers.Find the probability
thatitsatisfiestheinequality. x +
100
x
> 50
Q.20 3studentsAandBandCareinaswimmingrace.AandBhavethesameprobabilityofwinningandeach
is twice as likelyto win as C. Find the probabilitythat B or C wins.Assume no two reach the winning
pointsimultaneously.
Q.21 A box contains 7 tickets, numbered from 1 to 7 inclusive. If 3 tickets aredrawn from the box, one at a
time,determinethe probabilitythat theyare alternativelyeither odd-even-odd or even-odd-even.
Q.22 5 differentmarbles areplacedin5differentboxes randomly.Find theprobabilitythatexactlytwo boxes
remain empty. Giveneachbox can hold anynumberof marbles.
Q.23 SouthAfricancricketcaptainlost thetossofacoin13timesoutof14.Thechanceofthishappeningwas
(A) 13
2
7
(B) 13
2
1
(C) 14
2
13
(D) 13
2
13
Q.24 There areten prizes, fiveA's, three B's and two C's, placed in identical sealed envelopes for thetop ten
contestants inamathematics contest. Theprizes areawardedbyallowingwinners to selectan envelope
atrandomfromthoseremaining.When the8th contestantgoestoselecttheprize, theprobabilitythat the
remainingthree prizes are oneA, one B and one C, is
(A) 1/4 (B) 1/3 (C) 1/12 (D) 1/10

CLASS : XII (ABCD) DPP ON PROBABILITY DPP. NO.- 3
After 3rd Lecture
Q.1 Wheneverhorses a,b, cracetogether, their respectiveprobabilities ofwinning the race are 0.3, 0.5 and
0.2respectively.Iftheyracethreetimestheprobabilitythat“thesamehorsewinsallthethreeraces”and
the probablitythat a, b, c each wins one race, are respectively
(A)
8
50
;
9
50
(B)
16
100
,
3
100
(C)
12
50
;
15
50
(D)
10
50
;
8
50
Q.2 LetA& B be two events. Suppose P(A) = 0.4, P(B) = p & P(A B) = 0.7.The value of p for which
A & Bare independent is :
(A) 1/3 (B) 1/4 (C) 1/2 (D) 1/5
Q.3 A & B are two independent events such that P )
A
( = 0.7, P )
B
( = a & P(A  B) = 0.8, then, a =
(A) 5/7 (B) 2/7 (C) 1 (D) none
Q.4 A pair of numbers is picked up randomly (without replacement) from the set
{1, 2, 3, 5, 7, 11, 12,13, 17, 19}.The probabilitythat the number 11 was picked given that the sum of
the numbers waseven, is nearly:
(A) 0.1 (B) 0.125 (C) 0.24 (D) 0.18
Q.5 For abiased die the probabilities for the diffferent faces to turn up are given below :
Faces : 1 2 3 4 5 6
Probabilities: 0.10 0.32 0.21 0.15 0.05 0.17
Thedie istossed& youaretold that either faceone orface twohasturned up. Thenthe probabilitythat
it is faceone is :
(A) 1/6 (B) 1/10 (C) 5/49 (D) 5/21
Q.6 Adeterminantis chosenat randomfrom theset ofall determinants oforder2 with elements 0or1 only.
Theprobabilitythat thedeterminant chosenhas thevaluenonnegativeis :
(A) 3/16 (B) 6/16 (C) 10/16 (D) 13/16
Q.7 15 coupons are numbered 1, 2, 3,..... , 15 respectively. 7 coupons are selected at random one at a time
with replacement.The probabilitythat thelargest numberappearingon aselected coupon is 9 is :
(A)
6
16
9






(B)
7
15
8






(C)
7
5
3






(D) 7
7
7
15
8
9 
Q.8 A cardis drawn& replacedin an ordinarypack of52 playing cards.Minimum numberoftimesmust a
card be drawn so that there is atleast an even chance of drawing a heart, is
(A) 2 (B) 3 (C) 4 (D) morethan four
Q.9 An electrical systemhas open-closedswitches
S1, S2 and S3 as shown.
The switches operate independentlyof one another and thecurrent will flow fromAto B either if S1 is
closed or if both S2 and S3 are closed. If P(S1) = P(S2) = P(S3)=
2
1
, find theprobabilitythat the circuit
willwork.

Q.10 A certain team wins with probability0.7, loses with probability0.2 and ties withprobability0.1. The
team plays threegames. Findtheprobability
(i) that theteam wins at least twoof the games, but lose none.
(ii) that theteam wins at least one game.
Q.11 Anintegerischosenatrandomfromthefirst200positiveintegers.Findtheprobabilitythattheintegeris
divisible by6 or 8.
Q.12 Aclerkwasaskedtomailfourreportcardstofourstudents.Headdressesfourenvelopsthatunfortunately
paidno attentiontowhichreport cardbeput in whichenvelope.What is theprobabilitythat exactlyone
of the students received his (or her) own card?
Q.13 Find the probabilityof at most two tails or at least two heads in a toss of three coins.
Q.14 What is the probabilitythat ina group of
(i) 2 people, both will have the samedate of birth.
(ii) 3 people, at least 2 will have the same date of birth.
Assume the year to be ordinarryconsisting of 365 days.
Q.15 The probabilitythat a person will get an electric contract is
5
2
and the probabilitythat he will not get
plumbingcontractis
7
4
.Iftheprobabilityofgettingatleastonecontractis
3
2
,whatis theprobabilitythat
hewill get both?
Q.16 Five horses competein a race. Johnpicks two horses at random and bets on them.Find the probability
that Johnpicked the winner.Assume dead heal.
Q.17 Twocubeshavetheirfacespaintedeitherred orblue.Thefirstcubehas fivered faces andoneblueface.
When the two cubes are rolled simultaneously, the probability that the two top faces show the same
colour is 1/2. Number of red faces on the second cube, is
(A) 1 (B) 2 (C) 3 (D) 4
Q.18 A H and W appear for an interview for two vaccancies for the same post.
P(H) = 1/7 ; P(W) = 1/5. Find the probabilityof the events
(a) Both are selected (b) onlyone of them is selected (c) none is selected.
Q.19 A bag contains 6R, 4W and 8B balls. If 3 balls are drawn at random determine the probabilityof the
event
(a) all 3 are red ; (b) all 3 are black ; (c) 2 are white and 1 is red ;
(d) at least 1 is red ; (e) 1 of each colour are drawn
(f) the balls are drawn in the order of red, white, blue.
Q.20 The odds that a book will be favourablyreviewed bythree independent critics are 5 to 2, 4 to 3, and 3
to 4respectively.What is theprobabilitythat of thethree reviewsa majoritywill be favourable?
Q.21 In a purse are 10 coins, all five nP's except one which is a rupee, in another are ten coins all five nP's.
Ninecoinsaretakenfrom theformerpurseandputinto thelatter, andthen nine coins aretakenfromthe
latter and put into the former. Findthe chance that therupeeis still in the first purse.
Q.22 A, B, C in order cut a pack of cards, replacing them after each cut, on condition that the first who cuts
a spade shall win a prize. Findtheir respective chances.
Q.23 AandBinorderdrawfrom apursecontaining3 rupees and4nP's, find theirrespectivechances of first
drawing a rupee, the coins once drawn not being replaced.

CLASS : XII (ABCD) DPP ON PROBABILITY DPP. NO.- 4
After 4th Lecture
Q.1 There are n different gift coupons, each of which can occupyN(N > n) different envelopes, with the
same probability1/N
P1:TheprobabilitythattherewillbeonegiftcouponineachofndefiniteenvelopesoutofNgivenenvelopes
P2:Theprobabilitythattherewillbeonegiftcouponineachofnarbitraryenvelopesoutof Ngivenenvelopes
Considerthefollowingstatements
(i) P1 = P2 (ii) P1 = n
N
!
n
(iii) P2 =
!
)
n
N
(
N
!
N
n

(iv) P2 =
!
)
n
N
(
N
!
n
n

(v) P1 = n
N
!
N
Now,whichofthefollowingistrue
(A)Only(i) (B)(ii)and(iii) (C)(ii)and (iv) (D)(iii)and(v)
Q.2 Theprobabilitythatanautomobilewillbestolenandfoundwithingoneweekis0.0006.Theprobabilitythat
anautomobilewillbestolenis0.0015.Theprobabilitythatastolenautomobilewillbefoundinoneweekis
(A) 0.3 (B) 0.4 (C) 0.5 (D) 0.6
Q.3 Onebagcontains 3white& 2black balls, andanothercontains 2 white &3 black balls.Aball is drawn
from the secondbag& placedinthe first, thenaball is drawn from thefirst bag & placed in thesecond.
Whenthepairoftheoperationsis repeated, theprobabilitythat thefirst bagwill contain5 whiteballsis:
(A) 1/25 (B) 1/125 (C) 1/225 (D) 2/15
Q.4 A child throws 2 fair dice. If the numbers showing are unequal, he adds them together to get his final
score.Ontheotherhand,ifthenumbers showingareequal,hethrows2moredice&addsall 4numbers
showingtogethisfinal score. Theprobabilitythat hisfinal scoreis 6 is:
(A)
1296
145
(B)
1296
146
(C)
1296
147
(D)
1296
148
Q.5 A persondraws a card from a packof52cards, replaces it &shuffles the pack. Hecontinues doing this
till he drawsaspade. Theprobabilitythat hewill failexactlythefirst twotimes is :
(A) 1/64 (B) 9/64 (C) 36/64 (D) 60/64
Q.6 Indicate the correct order sequence in respect of the following :
I. Iftheprobabilitythatacomputerwillfailduringthefirsthourofoperationis0.01,thenifweturn
on100 computers, exactlyonewillfail in the firsthourofoperation.
II. Amanhastenkeysonlyoneofwhichfitsthelock. Hetriestheminadooronebyonediscarding
the one hehas tried. The probabilitythat fifth keyfits thelock is 1/10.
III. Given the eventsAand B in a sample space. If P(A) = 1, thenAand B are independent.
IV. Whenafairsixsideddieistossedonatabletop,thebottomfacecannotbeseen.Theprobability
that the product of the numbers on the five faces that can be seen is divisible by6is one.
(A) FTFT (B)FTTT (C) TFTF (D) TFFF
Q.7 An unbaised cubic die marked with 1, 2, 2, 3, 3, 3 is rolled 3 times. The probability of getting a total
score of 4 or 6 is
(A)
216
16
(B)
216
50
(C)
216
60
(D) none

Q.8 A bagcontains 3 R &3 G balls anda person draws out 3 at random. Hethen drops 3 blueballs into the
bag &again draws out 3 at random. The chancethat the 3 laterballs being all of different colours is
(A) 15% (B) 20% (C) 27% (D) 40%
Q.9 Abiasedcoin withprobabilityP,0<P<1, ofheads istosseduntil aheadappears forthefirsttime.Ifthe
probabilitythat the number of tosses required is even is 2/5 then the valueof P is
(A) 1/4 (B) 1/6 (C) 1/3 (D) 1/2
Q.10 If a, b  N then the probabilitythat a2 + b2 is divisible by5 is
(A)
9
25
(B)
7
18
(C)
36
11
(D)
17
81
Q.11 Inanexamination,onehundredcandidatestookpaperinPhysicsandChemistry.Twentyfivecandidates
failed in Physics only. Twentycandidates failed in chemistryonly. Fifteen failed in both Physics and
Chemistry.Acandidate is selected at random. The probability that he failed either in Physics or in
Chemistrybut notinbothis
(A)
20
9
(B)
5
3
(C)
5
2
(D)
20
11
Q.12 In a certain gameA's skill is to be B's as 3 to 2, find the chance ofAwinning 3 games at least out of 5.
Q.13 Ineachofaset ofgamesit is 2to1infavourofthewinneroftheprevious game. What isthechancethat
the playerwho wins the firstgameshall wins threeat least of the next four?
Q.14 A coinis tossed n times, what is thechancethat the head will present itself an odd number of times?
Q.15 Afairdieistossedrepeatidly.Awinsifitis 1or2ontwoconsecutivetossesandBwinsifitis3, 4, 5 or 6
ontwoconsecutive tosses.TheprobabilitythatAwins ifthedie is tossedindefinitely, is
(A)
3
1
(B)
21
5
(C)
4
1
(D)
5
2
Q.16 Counters marked 1, 2, 3 are placed in a bag, and one is withdrawn and replaced. The operation being
repeatedthree times, what is thechance of obtaininga total of 6?
Q.17 Anormalcoiniscontinuedtossingunlessaheadisobtainedforthefirsttime.Findtheprobabilitythat
(a) number of tosses needed are at most 3.
(b) number of tosses are even.
Q.18 A purse contains 2 six sided dice. One is a normal fair die, while the other has 2 ones, 2 threes, and 2
fives.Adieis pickedupandrolled. Becauseofsomesecret magneticattraction oftheunfairdie,thereis
75%chanceofpickingtheunfairdieanda25%chanceofpickingafairdie. Thedieisrolledand shows
up the face 3. The probabilitythat a fair die was picked up, is
(A)
7
1
(B)
4
1
(C)
6
1
(D)
24
1
Q.19 Before a race the chance of three runners,A, B, C were estimated to be proportional to 5, 3, 2, but
during the race Ameets with an accident which reduces his chance to 1/3. What are the respective
chance of B and C now?
Q.20 Afair coin is tossed a large number of times.Assuming the tosses are independent which one of the
followingstatement,isTrue?
(A)Oncethenumberofflipsislargeenough,thenumberofheadswillalwaysbeexactlyhalfofthetotal
number of tosses. For example, after 10,000 tosses one should have exactly5,000 heads.
(B) The proportion of heads will be about 1/2 and this proportion will tend to get closer to 1/2 as the
number oftosses inreases

(C)Asthenumberof tossesincreases, anylongrunofheads will bebalanced byacorrespondingrun of
tails so that the overall proportion of heads is exactly1/2
(D)All of the above
Q.21 A andBeach throw simultaneouslyapair of dice. Find theprobabilitythat theyobtain the same score.
Q.22 A is one of the 6 horses entered for a race, and is to be ridden byone of two jockeys B or C. It is 2 to
1thatB ridesA,inwhichcaseall thehorses areequallylikelyto win; if C ridesA, hischance is trebled,
whataretheodds against his winning?
Direction for Q.23 to Q.25
Let S andT are two events defined on a sample space with probabilities
P(S) = 0.5, P(T) = 0.69, P(S/T) = 0.5
Q.23 Events S and T are:
(A)mutuallyexclusive (B)independent
(C)mutuallyexclusiveandindependent (D)neithermutuallyexclusivenorindependent
Q.24 The value of P(S and T)
(A) 0.3450 (B) 0.2500 (C) 0.6900 (D) 0.350
Q.25 The value of P(S or T)
(A) 0.6900 (B) 1.19 (C) 0.8450 (D) 0

CLASS : XII (ABCD) DPP ON PROBABILITY DPP. NO.- 5
After 5th Lecture
Q.1 The first 12letters of the english alphabets are written down at random. The probabilitythat there are
4 letters betweenA& B is :
(A) 7/33 (B) 12/33 (C) 14/33 (D) 7/66
Q.2 Events A and C are independent. If the probabilities relating A, B and C are P (A) = 1/5;
P (B) = 1/6 ; P (A  C) = 1/20 ; P (B  C) = 3/8 then
(A) events B and C are independent
(B)events BandC aremutuallyexclusive
(C)events Band C areneitherindependentnormutuallyexclusive
(D) events B and C are equiprobable
Q.3 Assumethatthebirthofaboyorgirltoacoupletobeequallylikely,mutuallyexclusive,exhaustiveand
independent oftheotherchildrenin thefamily. Foracouplehaving6 children, theprobabilitythat their
"three oldest are boys" is
(A)
64
20
(B)
64
1
(C)
64
2
(D)
64
8
Q.4 Aand B playa game.Ais to throw a die first, and is to win if he throws 6, If he fails B is to throw, and
to win ifhe throws 6 or 5. If he fails,Ais to throw again and to win with 6 or 5 or 4, and so on, find the
chance of each player.
Q.5 BoxAcontains 3 red and 2 blue marbles while box B contains 2 red and 8 blue marbles.Afair coin is
tossed. If thecoin turns up heads, a marble is drawnfromA, if it turns up tails, a marbleis drawn from
bag B.The probabilitythat a red marble is chosen, is
(A)
5
1
(B)
5
2
(C)
5
3
(D)
2
1
Q.6 Aexaminationconsistsof8questionsineachofwhichoneofthe5alternativesisthecorrectone.Onthe
assumption that a candidate who has done no preparatorywork chooses for each question anyone of
thefive alternatives with equal probability, the probabilitythat hegets more than onecorrect answer is
equal to :
(A) (0.8)8 (B) 3 (0.8)8 (C) 1  (0.8)8 (D) 1  3 (0.8)8
Q.7 The germinationofseeds is estimatedbya probabilityof0.6.Theprobabilitythat out of11 sown seeds
exactly5or 6will springis :
(A)
11
5
5
10
6
5
C .
(B)
 
11
6
5 5
11
3 2
5
C
(C) 11C5
5
6
11





 (D) none of these
Q.8 Theprobabilityofobtainingmore tails than heads in6 tosses of afaircoins is :
(A) 2/64 (B) 22/64 (C) 21/64 (D) none
Q.9 Aninstrumentconsistsoftwounits.Eachunitmustfunctionfortheinstrumenttooperate.Thereliability
ofthefirstunitis0.9&thatofthesecondunitis0.8.Theinstrumentistested&fails.Theprobabilitythat
"onlythefirstunitfailed&thesecondunit issound"is:
(A) 1/7 (B) 2/7 (C) 3/7 (D) 4/7

Q.10 LotAconsists of 3G and 2D articles. Lot B consists of 4G and 1D article.Anew lot C is formed by
taking 3 articles from A and 2 from B. The probability that an article chosen at random from C is
defective,is
(A)
3
1
(B)
5
2
(C)
25
8
(D) none
Q.11 A die is weighted so that theprobabilityofdifferent faces to turn up is as given :
Number 1 2 3 4 5 6
Probability 0.2 0.1 0.1 0.3 0.1 0.2
If P (A/ B) = p1 and P (B / C) = p2 and P (C / A) = p3 then the values of p1, p2, p3 respectively are
Take the events A, B & C as A = {1, 2, 3}, B = {2, 3, 5} and C = {2, 4, 6}
(A)
3
2
,
3
1
,
4
1
(B)
3
1
,
3
1
,
6
1
(C)
4
1
,
3
1
,
6
1
(D)
3
2
,
6
1
,
4
1
Q.12 If mn coins havebeen distributed into m purses, ninto each find
(1) the chance that two specified coins will be found in thesame purse, and
(2) what thechancebecomes whenrpurses havebeen examined and found not tocontain eitherof
thespecifiedcoins.
Q.13 A box has four dice in it. Three of them are fair dice but the fourth one has the number five onall of its
faces.Adieis chosen at random from thebox andis rolled three times andshows up thefacefiveon all
the three occassions. The chance that the die chosen was a rigged die, is
(A)
217
216
(B)
219
215
(C)
219
216
(D) none
Q.14 OnaSaturdaynight 20%of alldriversinU.S.A.areundertheinfluenceofalcohol.Theprobabilitythat
adriver undertheinfluenceofalcoholwill havean accident is0.001. Theprobabilitythatasoberdriver
will havean accident is 0.0001. If a car on a saturdaynight smashed into a tree, theprobabilitythat the
driverwasundertheinfluenceofalcohol, is
(A) 3/7 (B) 4/7 (C) 5/7 (D) 6/7
Direction for Q.15 to Q.17 (3 Questions)
AJEEaspirantestimatesthatshewillbesuccessfulwithan80percentchanceifshestudies10hoursper
day, with a60 percent chance ifshe studies 7 hours per dayand with a 40 percent chanceif she studies
4 hours per day. She further believes that she will study 10 hours, 7 hours and 4 hours per day with
probabilities 0.1, 0.2 and 0.7, respectively
Q.15 Thechanceshewill besuccessful, is
(A) 0.28 (B) 0.38 (C) 0.48 (D) 0.58
Q.16 Given that she is successful, thechance she studied for4 hours, is
(A)
12
6
(B)
12
7
(C)
12
8
(D)
12
9
Q.17 Given that she does not achieve success, the chance she studied for 4 hour, is
(A)
26
18
(B)
26
19
(C)
26
20
(D)
26
21
Q.18 Therearefourballsinabag, butitisnotknown ofwhatcolourtheyare;oneballis drawnatrandom and
foundtobewhite.Findthechancethatall theballs arewhite.Assumeallnumberofwhiteball inthebag
tobeequallylikely. [Ans. 2/5]

Q.19 Aletterisknowntohavecomeeitherfrom LondonorClifton.Onthepostmarkonlythetwoconsecutive
letters ONare legible. What is the chance that it came from London?
Q.20 A purse contains n coins of unknown value, acoin drawnat random is found to be a rupee,what is the
chancethatisittheonlyrupeeinthepurse?Assumeallnumbersofrupeecoinsinthepurseisequallylikely.
Q.21 One of a pack of 52 cards has been lost, from the remainder of the pack two cards are drawn and are
found to be spades, find the chance that the missing card is a spade.
Q.22 A,Baretwoinaccuratearithmeticianswhosechanceofsolvingagiven questioncorrectlyare (1/8)and
(1/12) respectively.Theysolve a problem and obtained the same result. If it is 1000 to 1 against their
making thesame mistake, find thechancethat the result is correct.
Q.23 We conduct an experiment where we roll a die 5 times. The order in which the number read out is
important.
(a) What is thetotal numberof possibleoutcomesof this experiment?
(b) What is the probabilitythat exactly3 times a "2"appears in the sequence (sayevent E)?
(c) What is the probabilitythat the face 2 appears at least twice (sayevent F)?
(d) Which of the following are true : E  F, F  E?
(e) Compute the probabilities : P(E  F), P(E/F), P(F/E)
(f) Are the events E and F independent?

CLASS : XII (ABCD) DPP ON PROBABILITY DPP. NO.- 6
After 6th Lecture
Q.1 Abowlhas6redmarblesand3greenmarbles.Theprobabilitythat ablind foldedpersonwilldrawared
marble onthesecond drawfrom the bowl without replacingthe marble from thefirst draw, is
(A)
3
2
(B)
4
1
(C)
2
1
(D)
8
5
Q.2 5outof6personswhousuallyworkinanofficeprefercoffeeinthemid morning,theotheralwaysdrink
tea. This morningof the usual 6, only3 arepresent. The probabilitythat one of them drinks tea is :
(A) 1/2 (B) 1/12 (C) 25/72 (D) 5/72
Q.3 Pal’s gardner is not dependable, the probability that he will forget to water therosebush is 2/3.The
rose bushis in questionablecondition. Any how if watered, the probabilityofits withering is 1/2&if
notwateredthen theprobabilityof itswitheringis 3/4.Pal wentoutof station&afterreturninghe finds
that rose bush has withered. What is the probability that the gardner did not water the rose bush.
Q.4 Theprobabilitythat aradarwilldetect an object inone cycle is p.Theprobabilitythat theobject will be
detectedin ncycles is :
(A) 1  pn (B) 1  (1  p)n (C) pn (D) p(1 – p)n–1
Q.5 Nine cards are labelled 0, 1, 2, 3, 4, 5, 6, 7, 8. Two cards are drawn at random and put on a table in a
successive order, and then the resulting number is read, say, 07 (seven), 14 (fourteen) and so on. The
probabilitythat thenumberis even, is
(A)
9
5
(B)
9
4
(C)
2
1
(D)
3
2
Q.6 Two cards are drawn from a well shuffled pack of 52 playing cards one by one. If
A : the event that the second card drawn is an ace and
B : the event that the first card drawn is an ace card.
thenwhichofthefollowingistrue?
(A) P (A) =
17
4
; P (B) =
13
1
(B) P (A) =
13
1
; P (B) =
13
1
(C) P (A) =
13
1
; P (B) =
17
1
(D) P (A) =
221
16
; P (B) =
51
4
Q.7 If
2
p)
2
1
(
&
4
p)
1
(
,
3
p)
3
1
( 


are the probabilities of three mutually exclusive events defined on a
sample space S, then the true set of all values of p is
(A) 





2
1
,
3
1
(B) 





1
,
3
1
(C) 





3
1
,
4
1
(D) 





2
1
,
4
1
Q.8 Alot contains 50defective & 50 non defective bulbs .Two bulbs aredrawn at random, oneat a time,
with replacement . The events A, B, C are defined as :

A ={ the first bulbis defective}; B = { the second bulb is non defective}
C = { the two bulbs are both defective or both non defective}
Determinewhether (i)A,B,C arepair wise independent (ii)A,B,C are independent
Q.9 An Urn contains 'm' white and 'n' black balls.All the balls except for one ball, are drawn from it. The
probabilitythatthelast ball remainingintheUrniswhite,is
(A)
n
m
m

(B)
n
m
n

(C) !
)
n
m
(
1
 (D) !
)
n
m
(
n
m

Q.10 A Urn contains 'm' white and 'n' black balls. Balls are drawn one by one till all the balls are drawn.
Probabilitythatthesecond drawn ball is white, is
(A)
n
m
m

(B)
)
1
n
m
)(
n
m
(
)
1
n
m
(
n





(C)
)
1
n
m
)(
n
m
(
)
1
m
(
m




(D)
)
1
n
m
)(
n
m
(
mn



Q.11 Mr. Dupont isaprofessional wine taster.Whengiven aFrenchwine, he will identifyit with probability
0.9 correctlyas French, and will mistake it for a Californian wine with probability0.1. When given a
Californianwine,hewill identifyitwithprobability0.8correctlyasCalifornian, andwill mistakeitfora
Frenchwinewithprobability0.2.SupposethatMr.Dupontisgiventenunlabelledglassesofwine,three
withFrenchandseven withCalifornian wines. He randomlypicksaglass, tries thewine, and solemnly
says : "French".Theprobabilitythatthewinehetastedwas Californian, is nearlyequal to
(A) 0.14 (B) 0.24 (C) 0.34 (D) 0.44
Q.12 LetA, B & C be 3 arbitraryevents defined on a sample space 'S' and if,
P(A) + P(B) + P(C) = p1 , P(A  B) + P(B  C) + P(C  A) = p2 & P(A  B  C) = p3, then the
probabilitythatexactlyone of thethree events occurs is given by:
(A) p1  p2 + p3 (B) p1  p2 + 2p3 (C) p1  2p2 + p3 (D) p1  2p2 + 3p3
Q.13 Threenumbersarechosen at random without replacement from {1, 2, 3,...... , 10}.The probabilitythat
theminimumofthechosennumbers is3ortheirmaximumis7is
(A)
2
1
(B)
3
1
(C)
4
1
(D)
40
11
Q.14 A biased coin which comes up heads three times as often as tails is tossed. If it shows heads, a chip is
drawn from urn–I which contains 2 white chips and 5 red chips. If the coin comes up tails, a chip is
drawnfrom urn–IIwhichcontains 7 whiteand4 redchips.Given that ared chip was drawn, what is the
probabilitythat thecoin came up heads?
Q.15 In a college, four percent of the men and one percent of the women are taller than 6 feet. Further
60 percent of the students are women. If a randomly selected person is taller than 6 feet, find the
probabilitythat thestudent is awomen.
Q.16 Ifatleastone childinafamilywith3childrenisaboythentheprobabilitythat2ofthechildrenareboys,
is
(A)
7
3
(B)
4
1
(C)
3
1
(D)
8
3

Q.17 The probabilities of events,A B,A, B &A B are respectively inA.P. with probabilityof second
term equal to the common difference.Therefore the eventsAand B are
(A)compatible (B)independent
(C) suchthat one of them must occur (D) such that one is twice as likelyas the other
Q.18 From anurn containingsix balls, 3 white and 3 black ones,a personselects at random aneven number
of balls (all the different ways of drawing an even number of balls are considered equally probable,
irrespectiveoftheirnumber).Thentheprobabilitythattherewill bethesamenumberofblack and white
ballsamongthem
(A)
5
4
(B)
15
11
(C)
30
11
(D)
5
2
Q.19 One purse contains 6 copper coins and 1 silver coin ; a second purse contains 4 copper coins. Five
coins aredrawnfrom thefirstpurse andput intothesecond, and then2 coinsaredrawnfrom thesecond
andput into the first. Theprobabilitythat thesilvercoin is in the second purse is
(A)
2
1
(B)
9
4
(C)
9
5
(D)
3
2
Q.20 7 persons are stopped ontheroad at random andaskedabout theirbirthdays. Ifthe probabilitythat 3 of
them arebornonWednesday, 2onThursdayand theremaining2 onSundayis 6
7
K
, thenK isequal to
(A) 15 (B) 30 (C) 105 (D) 210
Q.21 TwobusesAandBarescheduledtoarrive atatowncentral busstation atnoon.Theprobabilitythat bus
A willbe late is 1/5.Theprobabilitythat bus Bwill be lateis 7/25. The probabilitythat the bus Bis late
given that busAis late is 9/10.Then the probabilities
(i) neither bus will be late on aparticularday and
(ii) busAis late given that bus B is late, are respectively
(A) 2/25 and 12/28 (B) 18/25 and 22/28 (C) 7/10 and 18/28 (D) 12/25 and 2/28
Q.22 Aboxcontains anormalcoinandadoublyheadedcoin.Acoinselected atrandomandtossedtwice,fell
headwise onboth the occasions. The probabilitythat the drawncoin is a doublyheaded coin is
(A)
2
3
(B)
5
8
(C)
3
4
(D)
4
5
Q.23 Abox contains 5 red and 4 white marbles.Two marbles are drawn successivelyfrom the box without
replacementandtheseconddrawnmarbledrawnisfoundtobewhite.Probabilitythatthefirstmarble is
alsowhileis
(A)
8
3
(B)
2
1
(C)
3
1
(D)
4
1
Q.24 A and B in order drawa marble from bagcontaining 5 white and 1 red marbles with the condition that
whosoeverdraws theredmarblefirst, winsthegame. Marbleoncedrawn bythem arenot replaced into
the bag.Thentheir respectivechancesof winning are
(A)
3
2
&
3
1
(B)
5
3
&
5
2
(C)
5
2
&
5
3
(D)
2
1
&
2
1

Q.25 In a maths paper there are 3 sections A, B & C. Section A is compulsory. Out of sections B & C a
student has to attempt any one. Passing in the paper means passing in A & passing in B or C. The
probabilityof the student passing inA, B & C are p, q & 1/2 respectively. If the probability that the
student is successfulis 1/2then:
(A) p = q = 1 (B) p = q =
2
1
(C) p = 1, q = 0 (D) p = 1, q =
2
1
Q.26 Abox contains 100 tickets numbered1, 2, 3,.... ,100.Two tickets are chosen at random. It is given that
themaximumnumberonthetwochosenticketsisnotmorethan10.Theminimumnumberonthemis5,
with probability
(A)
9
1
(B)
11
2
(C)
19
3
(D) none
Q.27 Sixteenplayers s1 ,s2 ,..... , s16 playin a tournament. Theyaredivided into eight pairsat random.From
eachpairawinneris decidedonthe basis ofagameplayed betweenthetwo players ofthe pair.Assume
that all the players are of equal strength. Theprobabilitythat "exactlyone of thetwo players s1 & s2 is
amongtheeightwinners"is
(A)
15
4
(B)
15
7
(C)
15
8
(D)
15
9
Q.28 The number 'a' is randomly selected from the set {0, 1, 2, 3, ...... 98, 99}. The number 'b' is selected
from the same set. Probabilitythat the number 3a + 7b has a digit equal to 8 at the units place, is
(A)
16
1
(B)
16
2
(C)
16
4
(D)
16
3
Q.29 We aregiven two urns as follows :
UrnAcontains 5 red marbles, 3 white marbles and 8 blue marbles.
Urn B contains 3 red marbles and 5 white marbles
Afairdiceistossedif3or6appears,amarbleischosenfromB,otherwiseamarbleischosenfromA.Find
theprobabilitythat(i)aredmarbleis chosen, (ii)awhitemarbleischosen,(iii)abluemarbleischosen.
(UseTree Diagram)
Q.30 We aregiven two Urns as follows :
UrnAcontains 5 red marbles,3 white marbles.
Urn B contains 1 red marbles and 2 white marbles.
Afair die is tossed, if a 3 or 6 appears, a marble is drawn from B and put intoAand then a marble is
drawnfromA; otherwise, a marbleis drawn fromAand put into B and then amarble is drawn from B.
(UseTree Diagram)
(i) What is the probabilitythat both marbles are red?
(ii) What isthe probabilitythat bothmarbles are white?
Q.31 Two boysAand Bfind the jumble of n ropes lyingon the floor. Each takes holdof one loose end.If the
probabilitythat theyare both holding the samerope is
101
1
then the number of ropes is equal to
(A) 101 (B) 100 (C) 51 (D) 50

Direction for Q.32 to Q.35 (4 Questions)
Read thepassagegivenbelow carefullybeforeattemptingthesequestions.
Astandarddeckofplayingcards has52cards.Therearefoursuit (clubs, diamonds,hearts andspades),
each of which has thirteen numbered cards (2, ....., 9, 10, Jack, Queen, King,Ace)
Inagameofcard,eachcardis worth anamountof points.Eachnumbered card is worthits number(e.g.
a 5is worth 5 points); the Jack, Queen and Kingare each worth 10 points ; and theAce is either worth
yourchoiceofeither1pointor11points.Theobjectofthegameistohavemorepointsinyoursetofcards
thanyouropponentwithoutgoingover21.Anyset ofcardswithsumgreaterthan21automaticallyloses.
Here's how thegame played.You and youropponent areeach dealttwo cards. Usuallythefirst card for
eachplayerisdealtfacedown,andthesecondcardforeach playerisdealt faceup.Aftertheinitial cards
are dealt, the first player has the option of asking for another card or not taking any cards. The first
playercankeepaskingfor morecards until eitherheorshegoes over21, in which casetheplayerloses,
or stops at some number less than or equal to 21. When the first player stops at some number less than
or equalto21, the second playerthen can take morecards until matchingorexceeding the first player's
numberwithout goingover 21, in which case the second player wins, or until goingover 21, in which
casethefirst player wins.
Weare goingtosimplifythegamea littleandassumethat all cards aredealtfaceup, so thatall cards are
visible.Assumeyouropponent is dealt cards and plays first.
Q.32 The chance that the second card will be a heart and a Jack, is
(A)
52
4
(B)
52
13
(C)
52
17
(D)
52
1
Q.33 The chance that the first card will be a heart or a Jack, is
(A)
52
13
(B)
52
16
(C)
52
17
(D) none
Q.34 Given that the first card is a Jack, the chancethat it will bethe heart, is
(A)
13
1
(B)
13
4
(C)
4
1
(D)
3
1
Q.35 Your opponent is dealt aKinganda10, and youare dealt aQueenand a9. Beingsmart, your opponent
does not takeanymore cards andstays at 20. Thechancethat you will win if you are allowed to take as
manycards as you need, is
(A)
564
97
(B)
282
25
(C)
188
15
(D)
6
1
More than one alternative are correct:
Q.36 If A& B are two events suchthat P(B)  1, BC denotes the event complementryto B, then
(A) P 
A BC
=
P A P A B
P B
( ) ( )
( )
 

1
(B) P (A  B)  P(A) + P(B)  1
(C) P(A) > < P 
A B according as P 
A BC
> < P(A)
(D) P 
A BC
+ P 
A B
C C
= 1

Q.37 Abaginitiallycontainsonered&twoblueballs.Anexperimentconsistingofselectingaballatrandom,
notingitscolour&replacingittogetherwith an additionalballof thesamecolour.Ifthreesuchtrialsare
made,then:
(A) probabilitythat atleast one blue ball is drawn is 0.9
(B) probabilitythatexactlyoneblueball is drawn is 0.2
(C) probabilitythat all the drawnballs are red giventhat all the drawnballs are of samecolour is 0.2
(D) probabilitythat atleast one red ball is drawn is 0.6.
Q.38 Two real numbers, x & yare selected at random. Given that 0  x  1 ; 0  y  1. LetAbe the event
that y2  x ; B be the event that x2  y, then :
(A) P (A  B) =
1
3
(B) A& B are exhaustive events
(C) A& B aremutuallyexclusive (D) A& B are independent events.
Q.39 For any two events A& B defined on a sample space ,
(A)  
P A B
P A P B
P B

 
( ) ( )
( )
1
, P (B)  0 is always true
(B) P  
B
A = P (A) - P (A  B)
(C) P (A  B) = 1 - P (Ac). P (Bc) , if A& B are independent
(D) P (A  B) = 1 - P (Ac). P (Bc) , if A& B are disjoint
Q.40 If E1 and E2 are two events such that P(E1) = 1/4, P(E2/E1) =1/2 and P(E1/ E2) = 1/4
(A) then E1 and E2 are independent
(B) E1 and E2 are exhaustive
(C) E2 is twice as likelyto occur as E1
(D) Probabilities of the events E1  E2 , E1 and E2 are in G.P.
Q.41 Let 0 < P(A) < 1 , 0 < P(B) < 1 & P(A  B) = P(A) + P(B)  P(A). P(B), then :
(A) P(B/A) = P(B)  P(A) (B) P(AC  BC) = P(AC) + P(BC)
(C) P((A  B)C) = P(AC). P(BC) (D) P(A/B) = P(A)
Q.42 If M & N are independent events such that 0 < P(M) < 1 & 0 < P(N) < 1, then :
(A) M & N aremutuallyexclusive (B) M & N are independent
(C) M & N are independent (D) P 
M N + P 
M N = 1