Formulas :

First digits = 1

Second digits = __ + __

Third digits = __ x __

Example :

18 × 15

First digits = 1

Second digits = 8 + 5

= 13

Third digits = 8 × 5

= 40

So, 18 × 15 = 270

Formulas :

First digits = 100 - [( 100 - 9__ ) + ( 100 - 9__ )]

Second digits = ( 100 - 9__ ) × (100 - 9__ )

Example :

97 × 96

First digits = 100 - [( 100 - 97 ) + ( 100 - 96 )]

= 100 - 7

= 93

Second digits = ( 100 - 97 ) × ( 100 - 96 )

= 12

So, 97 × 96 = 9312

35 × 122

35 = 1, 2, 4, 8, 16, 32, ...

122 = 122, 244, 488, 976, 1952, 3904, ...

35 = 1 + 2 + 32

So, 35 × 122 = 122 + 244 + 3904 = 4270

Formulas :

First digits = __ x __

Second digits = __ + __

Third digits = 1

Example :

31 × 51

First digits = 3 × 5

= 15

Second digits = 3 + 5

= 8

Third digits = 1

So, 31 × 51 = 1581

Formulas :

First 2 digits = [ __ x ( __ + 1)]

Last 2 digits = __²

Example :

95²

First 2 digits = [9 × ( 9 + 1 )]

= (9 × 10)

= 90

Last 2 digits = 5²

= 25

So, 95² = 9025

Formulas :

add 0 at the start and end of the number.

Example :

11 × 23125 = 0231250

Divide them to 2 in a group.

0 + 2 = 2

2 + 3 = 5

3 + 1 = 4

1 + 2 = 3

2 + 5 = 7

5 + 0 = 5

So, 11 × 23125 = 254375

Formulas :

add 0 at the start and end of the number.

Example :

13 × 326 = 03260

Divide them to 2 in a group.

( 3 + 0 ) + 3 = 3

( 3 + 3 ) + 2 = 11

( 3 + 2 ) + 6 = 12

( 3 + 6 ) + 0 = 18

So, 13 × 326 = 4238

Formulas :

( __ x __ )[( __ x __ ) + ( __ x __ )]( __ x __ )

Example :

51 × 63

( 5 × 6 )[( 5 × 3 ) + ( 1 × 6 )]( 1 × 3 )

(30)[( 15 + 6 )](3)

(30)(21)(3)

So, 51 × 63 = 3213

Example : 544 × 34

So, answer of 544 × 34 is 18496.

Formulas :

First 2 digits = [ __ x ( __ + 1)]

Last 2 digits = __ x __

Example :

93 × 97

First 2 digits = [9 × ( 9 + 1 )]

= 90

Last 2 digits = 3 × 7

= 21

So, 93 × 97 = 9021

Formulas :

First 2 digits = [( __ x __ ) + __ ]

Last 2 digits = __ x __

Example :

42 × 62

First 2 digits = [( 4 × 6 ) + 2]

= 26

Last 2 digits = 2 × 2

= 04

So, 42 × 62 = 2604