We call these small rectangles can surfaces , since they represent the inner surface area of the film canister. These can surfaces are our unit of area. In the second session, the students will measure the area of the base and the volume and analyze and discuss results. Since the base of the cylinder is a circle, areas are not simple. The best way to measure the area of the base is to outline the base on a piece of centimeter graph paper and count the squares enclosed.
Students measure volume using film canisters as their measuring cups.
One partner stands the cylinder on the plate, so that the plate forms a bottom, holding it in as round a shape as possible, and the other begins to pour in film canisters full of sand. As the sand goes in, its weight actually helps to make the cylinder round. If you are careful, very little sand will leak out of the bottom. Fill the cylinder to the top and record the number of cans that it holds. Students can answer this by trying it.