This Instructional Activity is a part of the Lesson 18, Unit 5, Grade 8. In this activity, students consider how the volume of a rectangular prism with a square base and a known height of 11 units changes if the edge lengths of the base triple. By studying the structure of the equation representing the volume function, students see that tripling the input leads to an output that is 9 times greater. In the following activity, students will continue this thinking with the volume function for cylinders. Identify students who make sketches of the two rectangular prisms or write expressions of the form 99s^2 or 11(3s)^2 to describe the volume of the tripled rectangular prism.