Multiplying 2-Digit Numbers by 11

Here’s our first MATH lesson. It is so easy that one night, I wound up showing it to everyone in the pizza restaurant. Well, everyone who would listen, anyway. We were scribbling down the answers right on the pizza boxes with such excitement that I couldn’t help it – I started laughing right out loud about how excited everyone was about math… especially on a Saturday night.

When you do this calculation in front of friends or family, it’s more impressive if you hand a calculator out first and let them know that you are ‘testing to see if the calculator is working right’.  Ask for a two digit number and have them check the calculator’s answer against yours.

If you really want to go crazy, you can have math races against the calculator and its operator, just as the Arthur Benjamin video shows.  (Only you don’t need to do the squaring of five-digit numbers in your head!)  Have fun!

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