Grade 6 Geometry: Volume of Prisms

Worked examples

Real problems from the practice worksheets, solved one step at a time.

1. Example 1

   A rectangular prism is 8 ft long, 6 ft wide, and 2 1/2 ft tall. What is its volume in cubic feet?

   1. Volume of a rectangular prism = length × width × height.
   2. Write the fractional edges as decimals: 2 1/2 = 2.5.
   3. 8 × 6 = 48.
   4. 48 × 2.5 = 120. The volume is 120 cubic feet.

   Answer: 120

2. Example 2

   A cube has edges of 1/2 ft. What is its volume in cubic feet? (Write your answer as a decimal.)

   1. Volume of a cube = edge × edge × edge.
   2. As a decimal, 1/2 = 0.5.
   3. 0.5 × 0.5 = 0.25.
   4. 0.25 × 0.5 = 0.125. The volume is 0.125 cubic feet.

   Answer: 0.125

3. Example 3

   The base of a rectangular prism has an area of 20 square feet. The prism is 1 1/2 ft tall. Use V = B × h. What is its volume in cubic feet?

   1. V = B × h: the base area times the height.
   2. As a decimal, the height is 1 1/2 = 1.5.
   3. 20 × 1.5 = 30. The volume is 30 cubic feet.

   Answer: 30