Calculation Tricks

Multiplication of Numbers near 100
e.g. 95 x 97 = x

100 - 95 = 5 & 100 - 97 = 3

First 2 digits = 95-3 or 97-5.

Last 2 digits = 5x3

... 95 x 97 = 9215

Multiplication of Numbers close to 10
e.g. 13x15 = x

Add 13 + 5 = 18

Multiply 3x5 = 15

... x = 195

Square of Numbers close to 100
(112)2

Difference = 12

Add 12 = 124

square 12 for last 2 digits = 144 (1 carry)

1122 = 12544

(96)2

Difference = 4

Subtract 4 = 92

Square 4 = 16

962= 9216

Division by 9
2231 / 9 =

247 Remainder = 8

Multiplication with 11
13 x 11 = 1_3

1+3 = 4

... 1_3 = 143

121 x 11 =

1_ _1

1 2 1 = 3 3

121 x 11 = 1331