Multiplying any two digit number by eleven is easier than most people think! Would you like to be able to calculate a math problem like this quickly in your head? Here is how to do it easily, mentally, and faster than you can enter it into a calculator!
Consider this Problem:
32 X 11
To solve this problem, simply add the digits 3 + 2 = 5, then put the 5 between the 3 and the 2, and there is your answer, 352.
Try another one:
53 x 11
Since 5 + 3 = 8, your answer is simply
NOW DON’T GET TOO EXCITED! Suppose the problem is 85 X 11? Even though 8 + 5 = 13, the answer is NOT 8135! As before, the 3 goes in between the numbers, but the 1 needs to be added to the 8 to get the correct answer of 935:
Think of it this way:
Here is another example: Try 57 x 11.
Since 5 + 7 = 12, the answer would be:
Now try this one as fast as you can: 77 x 11.
If you got the answer 847, then give yourself a high five! Now if you tell a friend or teacher that you can multiply, in your head, any two digit number by 11 it won’t be long before they ask you to do 99 x 11. Can you answer them?
Now if you are wondering if this method can be used for 3 or 4 digit (or larger) numbers by eleven, then wonder no more because it is!
If you have a problem like 314 x 11, the answer still begins with 3 and ends with 4. Since 3 + 1 = 4, and 1 + 4 = 5, the answer will be 3454.
I’ll blog more on the larger numbers at a different time, but for now, enjoy the new way of dazzling your friends and teachers with your new found, simple way to Math!
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Secrets of Mental Math