How many 1 inch cubes are needed to create a rectangular prism that is 6 inch long, 2 inch wide, and 3 inch high?

The area of the base is 5 inches times 3 inches, which equals 15 square inches. Thus 15 cubes are needed to make the bottom layer of the prism.

The prism is 4 inches high, so we will have 4 layers. The total number of cubes is 4 times 15, which is 60 cubes.

Reading Math

The formula for the area of the base is A = l * w or A = Iw.

Notice that in the example above we multiplied the length by the width to find the area of the base. Then we multiplied the area of the base by the height to find the volume.

Thinking Skill

Discuss

Does the order in which we multiply the dimensions change the answer? Why or why not?

We can calculate the volume V of a rectangular prism by multiplying the three perpendicular dimensions of the prism: the length l, the width w, and the height ft.

Thus the formula for finding the volume of a rectangular prism is V = l wh