Skill: Find volume using unit cubes

Volume tells how much space a solid takes up. We can find the volume of a rectangular prism by counting the unit cubes that fill it.

A unit cube has side lengths of 1 unit. Its volume is 1 cubic unit.

For a rectangular prism:

$$V=\ell \times w \times h$$

where $\ell$ is length, $w$ is width, and $h$ is height.

Example: A rectangular prism is filled with cubes. It is 4 cubes long, 3 cubes wide, and 2 cubes high. What is its volume?

1. Find the number of cubes in one bottom layer:

$$4 \times 3=12$$

There are 12 cubes in each layer.

2. Count the layers:

There are 2 layers, so multiply by the height:

$$12 \times 2=24$$

Or use the volume formula:

$$V=4 \times 3 \times 2=24$$

3. Include the correct units:

$$\boxed{24\text{ cubic units}}$$

The answer uses cubic units because we are measuring the space filled by three-dimensional cubes. Square units measure flat area, not volume.