As they did with cylinders in a previous lesson, in this lesson students compute volumes given radii and heights and find the radius or height given a cylinder’s volume and the other dimension by reasoning about the structure of the volume formula (MP7).

Next, they apply their understanding about the volumes of cylinders and cones to decide which popcorn container and price offers the best deal. This activity offers students the chance to reason about volume, out-of-scale images, and price per unit calculations. Students may use some or all of these ideas as they explain their reasoning and critique the reasoning of others for which container is the best deal (MP3).