I first came across this problem in Marilyn Burns’ book, *About Teaching Mathematics*. That book was really instrumental for me as I started to realize I wanted my math class to center around rich problems, that valued student sense-making.

I like this problem because it seems incredibly easy, but isn’t. I also really like that there are many different approaches/problem-solving strategies that students can use here. I often use it at the beginning of a semester to engage student in a conversation about how multiple approaches that come from them are both valuable *and* mathematical. Continue reading how Mark Trushkowsky used The Handshake Problem in class »