Lesson objective: Determine how many fractional-unit cubes it takes to fill a rectangular prism of a given volume.

This lesson provides an opportunity for students to apply their knowledge and understanding of volume to a real-life situation. Students are asked to determine how many 'Pow-R-Cubes' are needed to level up in a video game; the Pow-R-Cubes are different sizes and fill different-sized rectangular prisms.

Key Concept students will use:

- The formula for volume of a rectangular prism is connected to filling the prism with unit cubes.

Skills students will use:

- finding volume using V=lwh (Grade 5, Unit 9)
- fraction multiplication (Grade 5, Unit 7)

Students engage in Mathematical Practice 7 (Look for and Make Use of Structure) as they become more fluent in using fractional-edge-length cubes to fill rectangular prisms; for example once students identify that 8 half-unit cubes have a volume of 1 cubic unit, they can determine how many cubes will fill a prism of any other volume or dimensions.

**Key vocabulary: **

- cubic units
- half-unit cube
- rectangular prism
- whole-unit cube
- volume

**Special materials needed:**

- cm cubes or unit cubes from Base Ten Blocks to represent 'half-unit' or 'one-fourth-unit' cubes