Both numbers near but below 100

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

 

Example:

 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.

Example:

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