On Mondays we start class with a puzzle. When I read Sarah’s post on James Tanton’s math salute over the weekend I decided it would be a great puzzle to use! My students were willing to follow along (gotta love freshmen) and totally baffled when they got stuck at the end. (If you haven’t watched the video yet go do that now. Really.) Students tried. Declared it impossible. Tried again. Claimed they got it (by releasing their hands). Asked to watch the video again. Announced they never wanted to watch the video again. Claimed they got it (by going backwards from the ending position). Bingo! Everyone watch what that kid did! What a great idea to work backwards! The same student who said they never wanted to watch the video again asked if I could play it one more time. A few kids figured it out. They showed their neighbors. Everyone was engaged. It was great fun!
More than being fun, kids thought they were cheating by working backwards and I got to catch them being good. What a lovely way to introduce a powerful problem solving strategy early on in the year.