3 methods to multiply any number by 11 quickly

3 methods to Multiply any number by 11 quickly

 

 

 

 

 

 

 

In this article you are going to learn 3 methods to  multiply  any number by 11 quickly without using pen & paper.

Okay! Guys …This will be very short and sweet…

1st method:Normal process of Multiplication by 11

Let us take an example: 83*11

8    3

1     1

———————–

—–>8         3

8       3

9       1          3

so shift the number left by 1 digit and then add.

Take another example :456374*11

->4    5    6    3   7   4

4  5   6    3     7   4<—-shifted left by  1 digit.

———————–

5  0   2    0     1   1    4

2nd method:Mental multiplication by 11

This method is based on 1st method.Notice that whenever you multiply any number by 11.  you have added 8 and 3 to get 11 and carry was added to 8 to get 9.To multiply mentally any number by 11 we do the same mentally.

Example 67*11

67*11= 6  (7+6)  7= 6 (13) 7= 7 37

Example 96*11

96*11= 9  15     6   =  1056

Similarly, To multiply 3 digit number with 11

Take an example 347*11

347*11=   3  3+4  4+7  7  =        3      12         11     7 =   4   3  1 7

1 is taken carry from 11 and added to 12 = 13 ,again 1 is taken carry from 13 and added to 3 to get 4.

To multiply four digit number by 11

4538*11=4 9  9 18, we go through the same process of adding neighborhood digits.

You can apply the same process for higher numbers as well.

Can you solve this mentally?

567238442*11 ?

3 rd method : Mental multiplication by 11.

Let us take an example 56*11

56*11=56(10+1)=560+56=560+40+16=616

We have taken 11 as 10+1 and then multiplied to 56, to add 560 and 56 ,take 40 from 56 and give to 560.

Now, if any number is given to you first multiply by 10 then add the original number to the result of multiplication by 10.

Let us take an example:468*11

Like 468*11=4680+468=4000+600+80+400+60+8= 4000+600+400 +80+60+8=5000+140+8=5148

To understand above process in more details read my Mental Addition Trick- Learn Within 5 Minutes.

Basically we think of number in thousands, hundreds and multiple of 10, then add corresponding thousands and hundreds.

This 3rd method is so much general that you can apply and memorize multiplication table fast.You can read my article  How to Memorize Multiplication Table Fast- Table up to 99*99 if you haven’t read yet.

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Niraj Tulsyan
Btech in Electronics & Communication.I love Maths, Science & Technology.