Suppose we want to multiply two numbers X and Y which are near and below 100.
Then,
Where, D1 = X – 100 and D2 = Y – 100
Then product of X and Y can be obtained using following trick:
X+D2|D1xD2 or Y+D1|D1xD2
Multiply 95 and 96
Solution:
D1 = 95 – 100 = -5 and D2 = 96 – 100 = -4
Then
X + D2|D1*D2
=95 + (-4)|(-5)x(-4)
=95-4|20
=9120
Note: D1xD2 should always be a 2 digit number. if it is single digit then add ’0’ before that digit.
Multiply 97 and 98
Solution:
Here D1 = 97 – 100 = -3 and D2 = 98 – 100 = -2
Then,
X + D2|D1xD2
=97 + (-2)|(-3)x(-2)
=97 – 2|06
(here (-3)x(-2) is single digit so we added o before it)
=9506