This problem is an early version of Dan’ Meyer’s three-act math tasks. It requires a few styrofoam cups but is a really nice hands-on problem for students and conveys an appreciation for the effect that the rate of change and starting amount have in a function rule. It is great for helping students understand the difference between the two. This write-up has a step-by-step progression for teachers to follow, along with some good questions to help students think about what is going on as well as a few really nice extension activities.