Unit Pretest

A rectangular prism has a height of 12 cm and a square base with sides measuring 5 cm. A pyramid with the same base and [tex]\(\frac{1}{2}\)[/tex] the height of the prism is placed inside the prism. What is the volume of the space outside the pyramid but inside the prism?

A. [tex]\(50 \, \text{cm}^3\)[/tex]

B. [tex]\(150 \, \text{cm}^3\)[/tex]

C. [tex]\(200 \, \text{cm}^3\)[/tex]

D. [tex]\(250 \, \text{cm}^3\)[/tex]



Answer :

To solve this problem, let's break it down step-by-step:

1. Calculate the volume of the rectangular prism:

- The base of the prism is a square with sides measuring 5 cm.
- The height of the prism is 12 cm.
- The volume [tex]\(V_{\text{prism}}\)[/tex] of a rectangular prism is given by the formula:
[tex]\[ V_{\text{prism}} = \text{base area} \times \text{height} \][/tex]
Since the base is a square:
[tex]\[ \text{base area} = \text{side}^2 = 5 \times 5 = 25 \, \text{cm}^2 \][/tex]
Therefore:
[tex]\[ V_{\text{prism}} = 25 \, \text{cm}^2 \times 12 \, \text{cm} = 300 \, \text{cm}^3 \][/tex]

2. Calculate the volume of the pyramid:

- The pyramid has the same base as the prism, which is a square with side 5 cm.
- The height of the pyramid is half the height of the prism, which is:
[tex]\[ \text{height of pyramid} = \frac{12}{2} = 6 \, \text{cm} \][/tex]
- The volume [tex]\(V_{\text{pyramid}}\)[/tex] of a pyramid is given by the formula:
[tex]\[ V_{\text{pyramid}} = \frac{1}{3} \times \text{base area} \times \text{height} \][/tex]
Using the previously calculated base area of 25 cm²:
[tex]\[ V_{\text{pyramid}} = \frac{1}{3} \times 25 \, \text{cm}^2 \times 6 \, \text{cm} \][/tex]
Simplifying:
[tex]\[ V_{\text{pyramid}} = \frac{1}{3} \times 150 \, \text{cm}^3 = 50 \, \text{cm}^3 \][/tex]

3. Calculate the volume of the space outside the pyramid but inside the prism:

- To find this volume, subtract the volume of the pyramid from the volume of the prism:
[tex]\[ \text{space volume} = V_{\text{prism}} - V_{\text{pyramid}} \][/tex]
Using the volumes calculated above:
[tex]\[ \text{space volume} = 300 \, \text{cm}^3 - 50 \, \text{cm}^3 = 250 \, \text{cm}^3 \][/tex]

The volume of the space outside the pyramid but inside the prism is:
[tex]\[ 250 \, \text{cm}^3 \][/tex]

Therefore, the correct choice is:
D. 250 cm³