I stole another idea from my math coach1.
After the quiz today, I gave the kids a bit of relief, and used the built in camera on my new laptop to set up a recording area, and had those kids who wanted to show off walk forwards & backwards (with big arrow signs pointing in the direction they were walking).
I then spent about 4 hours wrestling with Quicktime & iMovie & Keynote, with the end result that my culminating slide has 4 simultaneous videos with kids walking forwards & backwards, and the same videos reversed, arranged in the typical +/- multiplication grid, and it’s very obvious that – * – gives the same result as + * +, while + * – looks the same as – * +.
I’d post a video version of it here, except that I’m tired of wrestling with moving images, and it’s nigh on driving me nuts at this point.
Hopefully I’ll be able to jiggle it so my poor processor can keep up…
1 That’s what coaches are for, right?