Multiplication by 11

Leadership and learning are indespansable to each other  
                                                                           - John F Kennedy

Note:  All these tricks applicable for below 100. We can extend these tricks to above 100 with slight modification  in the formula. Some tricks applicable without modifications also.

Let me recall tricks for multiplication with 5 and 9

Ex : 48 x 5 = ?
       step 1 : 48 / 2 = 24
       step 2 : 24 x 10 = 240
       Therefore 48 x 5 = 240

Ex : 48 x 9 = ?
 From now onwards we will follow the following notation :     
 .../1000's digit / 100's digit/ 10's digit/ 1's digit

So 48 x 9

1's digit         : 10 -8 = 2
10's digit       :  48 - 4 - 1  = 43
In the result (43)  10's digit is 3
4 becomes 100's digit

Therefore 48 x 9 = 432

If you have any confusion, please refer the formula in previous post.

Multiplication with 11 :

11 table song 


This is very easy. Multiplication by 11 is adding the digits in the number.

Lets see how this works 

Ex1 : 23 x 11 = ?

Remember the notation as I mentioned above 
 
1's digit : 3
10's digit : 2 + 3 = 5
100's digit : 2

So 23 x 11 = 253

Ex2 : 49 x 11 = ?
1'digit : 9
10's digit : 4 + 9 = 13
100's digit : 4

So 49 x 11 = 4 / 13 / 9
                  = 539 ( 1 carry forward to hunderds in 13. so 4 + 1 = 5 )

Ex3 : 54 x 11 = ?

Ex4 : 74 x 11 = ?

Practice above examples.

Happy Learning ...