This document provides examples of multiplying two numbers close to 100 using the base 100 method. It demonstrates: 1) Multiplying 88 x 98 by writing them as distances from 100, getting 8600, then adding the adjustment of 12 x 2 = 24, for a total of 8624. 2) Multiplying 102 x 104 by writing them as distances from 100, getting 10600, then adding the adjustment of -2 x -4 = 8, for a total of 10608. 3) Multiplying 97 x 102 with one number below and one above 100, getting 9900, then subtracting the adjustment of 3 x -2 = -6, for a total of 9894.

1. Coffee Math:
Methods,
Tips And Tricks
Series.
By
Puwork Utara
May 2011

2. Multiplying
2 Numbers
Close to 100
They are in the base 100.
Hence the reference point
(base) will be 100.

3. 88 X 98 = ______
Both numbers
are close to 100
but less than 100

4. 88 X 98 = ______
88 +12 100
98 +2
100

5. 88 X 98 = ______
88 +12 100
98 +2
100
Either ( 88 - 2 ) X 100 = 8600
Or ( 98 - 12 ) X 100 = 8600

6. 88 X 98 = ______
88 +12 100
98 +2
100
Either ( 88 - 2 ) X 100 = 8600
Or ( 98 - 12 ) X 100 = 8600
And 12 X 2 = 24

7. 88 X 98 = ______
88 +12 100
98 +2
100
Either ( 88 - 2 ) X 100 = 8600
Or ( 98 - 12 ) X 100 = 8600
And 12 X 2 = 24
Last 8600 + 24 = 8624 #

8. 102 X 104 = ______
Both numbers
are close to 100
but more than 100

9. 102 X 104 = ______
102 -2 100
104 - 4
100

10. 102 X 104 = ______
102 -2 100
104 - 4
100
Either ( 102 + 4 ) X 100 = 10600
Or ( 104 + 2 ) X 100 = 10600

11. 102 X 104 = ______
102 -2 100
104 - 4
100
Either ( 102 + 4 ) X 100 = 10600
Or ( 104 + 2 ) X 100 = 10600
And -2 X -4 = + 08

12. 102 X 104 = ______
102 -2 100
104 - 4
100
Either ( 102 + 4 ) X 100 = 10600
Or ( 104 + 2 ) X 100 = 10600
And -2 X -4 = + 08
Last 10600 + (+08) = 10608 #

13. 97 X 102 = ______
One of the numbers
is less than 100 and
the second number
is more than 100

14. 97 X 102 = ______
97 +3 100
102 - 2
100

15. 97 X 102 = ______
97 +3 100
102 - 2
100
Either ( 97 - ( -2)) X 100 = 9900
Or ( 104 - 3 ) X 100 = 9900

16. 97 X 102 = ______
97 +3 100
102 - 2
100
Either ( 97+ 2 ) X 100 = 9900
Or ( 104 - 3 ) X 100 = 9900
And +3 X (-2 ) = - 06

17. 97 X 102 = ______
97 +3 100
102 - 2
100
Either ( 97+ 2 ) X 100 = 9900
Or ( 104 - 3 ) X 100 = 9900
And +3 X (-2 ) = - 06
Last 10600 + (- 06 ) = 9894 #

18. END