This CUBE AND STACK PUZZLE asks student teams of four to classify real numbers. Each student gets a different cube template (1 of 4). Each student in the team cuts out and constructs their cube. They then work together to stack their 4 cubes so that 4 facing sides describe a type of real number including integers, whole numbers, rational numbers, and counting numbers. It is challenging, but my students think it's fun. I've used this activity for review, to teach a concept after a brief intro