I have to credit our babysitter Alison for this post, as she taught Bart (and me) something new this week. Bart started playing a computer game, Timez Attack, which helps kids learn their times tables (look for a review coming soon). He ran out of the office yelling “Mommy! What’s 9 times 8?!” Before I could answer, Alison calmly intervened to ask him “Bart, do you remember the 9’s trick?” Then he ran back to the office and resumed his game with no further questions.

Later, after Alison went home, I just had to ask “So what is ‘The 9’s Trick’?” He explained it to me in about 30 seconds. It’s very simple and easy to remember, but I had never seen it before so I assume it will be new to some of you reading this too. Here goes…

Use this trick to multiply 9 times any number from 1-9. Hold your 10 fingers out in front of you. Now, say you want to know 9 X 5. Starting from the left, count 5 fingers and put the 5th finger down. Now the number of fingers to the left of the lowered finger is the first digit of the answer, and the number of fingers to the right of the lowered finger is the second digit of the answer. Here’s a picture:
Picture
For another example, consider 9 X 8:
Picture
Another thing to notice about this “trick” is that the two digits that comprise the answers to “times 9” problems also sum to 9. For example:

 2 X 9 = 18 ... and... 8 + 1 = 9

3 X 9 = 27 ... and... 2 + 7 = 9

4 X 9 = 36 ... and... 3 + 6 = 9, and so on….

Of course kids eventually have to memorize the times tables, there’s no getting around it. However, isn’t this a nice method to have as back-up during the learning process, or if your child is not sure and needs a way to double-check their answer, or if you just suddenly blank on what is 9 X 6? (I know it’s happened to at least some of you, especially any readers who are, or have been, pregnant.) 

When I was a kid I didn’t learn a lot of math tricks, did you? This kind of thing wasn’t taught in school so number tricks weren’t even on my radar.  Now with the internet I can look up all sorts of cool stuff and shortcuts I would have never discovered on my own.  I even have an iPhone app called Math Tricks  that I *will* get around to using some day!

A lot of the tricks you find are not all that useful and are hard to remember if you don’t practice regularly, but they really are fascinating.  Even if you don’t consider yourself to be a “math person,” look up a few easy tricks online and I am confident you will gain at least an incremental appreciation for the beauty of numbers.

Now that you know “The 9’s Trick,” can you picture yourself sharing this at a cocktail party (not that I’ve been to one recently) or how about an elementary school social (which I have attended recently)? You can ask your co-workers if they’ve heard of “The 9’s Trick” and enlighten those who are still unaware.  Alternatively, if you’re not ready to publicly spread the word about The 9’s Trick, then how about sharing it tonight at the dinner table? Π
Hilary Mulligan
03/07/2011 20:35

Jenny! The 9's trick is super cool. Jeff and I just practiced several scenerios and we got it! :-)

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03/10/2011 15:53

Hey Jen - We know an awesome song about this - I bet the kids would like it! Our Brazilian au pair, Debbie, turned us on to the famed Brazilian kids' performer, Xuxa. She has a song (in Portuguese but you can still get the drift) all about this. I found it on You Tube. Check it out!

http://www.youtube.com/watch?v=e-yAjv9IHRg

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03/10/2011 16:00

OK, so I posted it before I realized that the explanation with the 9's trick is missing in this version. We have it on DVD and it explains the trick via fingers. Too bad it's missing on you tube :(

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03/10/2011 16:57

Love the video - the woman looks a little like Wanda's K teacher :)

Hi Hilary! I'm glad you liked the "trick". Feel free to use to impress some donors on your next trip :)

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