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Solution key: Inside the box

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Camp · Inside the box

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1 of 8 · volume-c01

A rectangular prism is 5 by 3 by 4. What is the volume?

  1. Volume of a rectangular box is length times width times height. That is how much fits inside.
  2. 5 times 3 is 15.
  3. 15 times 4 is 60.
  1. The volume is 60.
  2. Check: 60 ÷ 4 (the height) = 15, and 5 × 3 = 15, so it matches. Volume uses cubic units.

Answer: 60 cu units

2 of 8 · volume-c02

A prism has base area 12 and height 7. What is the volume?

  1. A prism uses V = base area times height. B is the area of the base, not a side length.
  2. The base area is already 12, and the height is 7.
  3. 12 times 7 is 84.
  1. The volume is 84.
  2. Check: 84÷7=12, the given base area; volume uses cubic units.

Answer: 84 cu units

3 of 8 · volume-c03

A rectangular pyramid has base 6 by 4 and height 9. What is the volume?

  1. A pyramid holds one third of a prism with the same base and height. Do not skip the one third.
  2. The base is 6 × 4 = 24 square units. Multiply by height 9: 24 × 9 = 216 cubic units for a matching prism.
  3. One third of 216 is 72. Same as (1/3) times 24 times 9.
  1. The volume is 72.
  2. Check: Three volumes of 72 total 216, the matching prism volume.

Answer: 72 cu units

4 of 8 · volume-c04

A pyramid has base area 15 and height 6. What is the volume?

  1. This is a pyramid, so multiply base area times height, then take one third.
  2. 15 times 6 is 90.
  3. One third of 90 is 30.
  1. The volume is 30.
  2. Check: 30×3=90, the amount before taking one third.

Answer: 30 cu units

5 of 8 · volume-c05

A rectangular prism is 2 by 3 by 6. What is the total surface area?

  1. Total surface area is the wrapping: every face, front and back.
  2. The three different face areas are 2 times 3, 2 times 6, and 3 times 6, which are 6, 12, and 18.
  3. Those add to 36, and the opposite faces double it: 2 times 36 is 72.
  1. The surface area is 72.
  2. Check: The six faces total 6+6+12+12+18+18=72 square units.

Answer: 72 sq units

6 of 8 · volume-c06

A cube has edge 4. What is the volume?

  1. A cube has the same length on every edge.
  2. Volume is edge times edge times edge.
  3. 4 times 4 times 4 is 64.
  1. The volume is 64.
  2. Check: One 4-by-4 layer is 16; four layers total 64 cubic units.

Answer: 64 cu units

7 of 8 · volume-c07

A cube has edge 5. What is the total surface area?

  1. A cube has 6 square faces.
  2. Each face is 5 by 5, so 25.
  3. 6 times 25 is 150.
  1. The surface area is 150.
  2. Check: 150÷6=25, the area of one 5-by-5 face.

Answer: 150 sq units

8 of 8 · volume-c08

A triangular prism has base area 10 and length 8. What is the volume?

  1. For this triangular prism, multiply the area of a triangular end by the length between the two triangular ends.
  2. The base area is 10 square units, and the prism length is 8 units: 10 × 8 = 80 cubic units.
  3. Do not use the one-third. That rule is only for a pyramid.
  1. The volume is 80.
  2. Check: 80 ÷ 8 = 10, which matches the triangular base area we were given.

Answer: 80 cu units