INSTANT MULTIPLICATION BY ELVEN

INSTANT MULTIPLICATION BY ELVEN

Let’s begin with one of my favorite feats of mental math—how to multiply, in your head, any two-digit number by eleven. It’s very easy once you know the secret. Consider the problem:

32 *11

To solve this problem, simply add the digits, 3+2 =5

put the 5 between the 3 and the 2, and there is your answer:  352

What could be easier? Now you try:

53 *11

Since 5 +3 =8, your answer is simply

583

One more. Without looking at the answer or writing anything down, what is

81 =11?

Did you get 891? Congratulations!

Now before you get too excited, I have shown you only half of what you need to know. Suppose the problem is

92*11

Although

9+2=11

 1

 9 1 2

1012

Okay, take a moment to practice your new skill a few times, then start showing off. You will be amazed at the reaction you get. (Whether or not you decide to reveal the secret is up to you!)

Welcome back. At this point, you probably have a few questions, such as:

“Can we use this method for multiplying three-digit numbers (or larger) by eleven?”

Absolutely. For instance, for the problem 314 *11, the answer still begins with 3 and ends with 4. Since 3 +1 =4, and

1+4=5, the answer is 3454