In this lesson, students reason about the volume of various rectangular prisms, solidifying their understanding that multiplying the edge lengths, or the area of the base and the height of a prism, gives its volume. Students also have an opportunity to reason in the opposite direction: to find an unknown edge length by dividing the volume by other two edge lengths or by the area of the base.

Problems about prisms may involve three quantities—area of the base, height, and volume—or four quantities—length, width, height, and volume. To find an unknown length may involve calculating two quotients. For instance, to determine an unknown height may mean dividing the volume by the length and then by the width. It may also mean two different operations, for example, multiplying two known lengths first and then dividing the volume by that product. In tackling problems with increasing complexity, students must make sense of problems and persevere in solving them (MP1).