Day 65 – Bathtub Problem

Math 8 – Today students worked on the bathtub problem. It was totally solvable and as a result we saw a lot of success. The problem was difficult enough to stimulate discussion and reveal initial misconceptions though. Most groups first thought the solution would be 45 minutes. I think the logic was that if you add an hour and 30 minutes and then average/split it between two, you get 45 minutes. Listening to student conversations, there would inevitably be someone who would speak up and say something like, “That doesn’t make sense! If you use just hot water it only takes 30 minutes, it can’t take longer by adding even more water!”