## Tuesday, February 26, 2013

### Trick to multiply 2 digit number with 11 verbally

In this post i will show you how to multiply any two digit number with 11 verbally.
I am using term secondary number here for the number that we will multiply with 11
In 11*11  11 is secondary number
12*11  12 is secondary number
13 * 11  13 is secondary number

11*11 = 121

right most digit is the first number of the digit  your multiplying here it is 1
middle digit is sum of  of both number you are multiplying with 11 is 1+1 = 2
last digit is  the one plus the carry if exist  from second number on from middle digit here it is  1

11*13 = 143

right most digit is the first number of the secondary number 3
middle digit is sum of  of both number you are multiplying with 11 is   (1+3)    4
last digit is  the one plus the carry on from middle digit here it is             1

11 * 14 = 154
right most digit is the first number secondary number here it is  4
middle digit is sum of  of secondary number   ( 4 + 1) = 5
last digit is  the one plus the carry if exist  from second number on from middle digit here it is 1

Lets try bigger number

11* 24
right most digit is the first number secondary number 4
middle digit is sum of secondary number    ( 4 + 2) =6
last digit is  the one plus the carry if exist  from second number on from middle digit here it is 2

so the answer is  264

11 * 89
right most digit is the first number secondary number9
middle digit is sum of secondary number    (8+9) = 17
ast digit is  the one plus the carry if exist  from second number on from middle digit here it is 8+1 = 9