This Instructional Activity is a part of the Lesson 10, Unit 5, Grade 8. We will continue with an intuitive discussion of volume. Demonstrate the volume of a rectangular prism using a stack of note cards. The volume of the rectangular prism increases as the height of the stack increases. Note that the rectangles (note cards) are congruent. Referring to the picture, we call the blue rectangle at the bottom of the rectangular prism the base, and the length of any one of the edges perpendicular to the base the height of the rectangular prism.