How to multiply a 2 digit number by 11

by Chuck Heintzelman on May 1, 2012

“If you think dogs can’t count, try putting three dog biscuits in your pocket and then giving Fido only two of them.”
~Phil Pastoret

Today is Random Tidbit Tuesday at StoryChuck, where I post something I find strange but interesting.

It’s amazingly easy to multiply 11 by any two digit number if you use the following trick.  Split the number apart, add them together, and stick the sum in the middle.

To illustrate. Let’s say you have 52 X 11

Super simple, huh?  Now what happens if the number you add together is 10 or greater?  It’s still pretty easy, you just need to add another step and bump the first digit by one.

So we’ll say we have 58 X 11

Here’s a couple more examples:


This simple trick makes multiplication by 11 a snap.