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Mental Math Shortcut Multiplying by 11

How do we multiply by eleven easily?

First we will try this by writing the answer backwards.

So, when always multiplying a large number by 11, the last number will always be the last number of the sum we are multiplying.

Let me explain.

176 is the number we are multiplying.

So the last number in out answer will be 6. If the sum was 143 the last number in our answer would be 3… get it?

So now what?

Easy, just add the next number to the last number, 7 + 6 = 13

So the next last number will be 3, carry the 1.

Add the 7 and 1 together, giving 8, then add the carried 1, 9 then write that number as our next part of the answer, 936

Then, the last number will be the first number in our sum, in this case 1.

So the answer is 1936.

Try 278Last number is 8

7 + 8 = 15

Second last number is 5, carry the 1

7 + 2 = 9 add the carried 1, 10

Third last number is 0, carry the 1

Add the carried 1 to the first number in the sum, 2 giving:

2 + 1 = 3

So the answer is 3058!

Alternatively, you could always just add a zero to the number you are multiplying and then add the original number to it again…

156 X 11

try it this way:

Add a zero to the end

1560

Add 156 to this

1560 + 156 = 1716

Whatever method works best, stick to it!

This entry was posted on Friday, June 22nd, 2007 at 8:18 am and is filed under Mental Tips & Tricks, Vedic Maths. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

6 Responses to “Mental Math Shortcut Multiplying by 11”

  1. This was really interesting. I liked it.

  2. Another way of doing it will be
    1] 76 X 11
    write the digit with space in between like
    7 6
    now add both of them 7+6=13
    write 13 in between them
    7 13 6
    now carry 1 from 13 to 7 and add it.you get
    836 the answer.
    2] 176 x 11
    17 6
    17+6=23
    17 23 6
    17+2 = 19
    so we get
    1936 the answer.

  3. gr8888888888888888888888888888888888ttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttttt

  4. If you would like to see an animation of this contact me. Remember a picture is worth a thousand words, a movie maybe a google away.

  5. How to do the same for 7895 x 11?

  6. For getting the answer of 7895*11 :
    The steps are as follows

    1) Divide 7895 in 2 partitions as 789 5
    2) 789+ 5 = 794
    3) 79 is carry which is to be added in 789 to give 789 + 79 =868 Thus we get the first part of answer as 868, second part 4, third part 5
    Therefore the final answer is 86845

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