A Physical Game for Factoring and Primes: Groups! (Plus: Math for Love grows)

January 10, 2011

I’ve been out of touch on the old web-log lately, but after a three week hiatus, I’m back!

If you glance at the rest of the site, you might notice that there’s another person working with me. I haven’t officially announced it here yet, so I will now: the exceptional Katherine Cook has joined Math for Love. She’s going to be co-teaching, tutoring, consulting, and blogging here soon. (I’m a huge fan of her previous blogging.) I’m thrilled to have her working with me.

I’ve also got a great game to share. Katherine and I had a one day math circle in December, and came up with a really cool group activity for kids: a kind of factoring-based musical chairs. It’s called:


Rules: You need space to move around. The kids all stand up, and you call out different numbers (Three!). The kids, then, have to get into groups of that size. If there’s an odd person or two out, well, they lose that round, but the winning and losing doesn’t matter–just move on to a different number. You can hit numbers you’ve called before.

Now here’s what makes it interesting: we played with 12 kids, and virtually every number we called out–2, 3, 4, 6, 1, 12 (one big group!)–no one was cut out. When we called five, though, that ended–two people were left out when the groups formed. But then one of us joined in, making the whole group equal to 13, and suddenly there was practically no number we called that didn’t leave someone out!

A fun game, with a mystery underneath. We played with K-2nd graders (plus some parents), and we’re going to be continuing with an 8 week circle which will delve into this mystery. Why do some numbers break up nicely, and others always leave someone groupless? How can you tell which numbers will do what?

For every age, there’s an appropriate mystery. Prime numbers and division are appropriate for virtually every age.

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