Question

Use the image to answer the question.

An illustration shows an equilateral triangle with each side measuring 6 centimeters. The perpendicular height is shown as a dashed line from the base to the apex and and is 4 centimeters. A right angle symbol is shown to the right of the perpendicular line.

Use the model for the base of a triangular prism and triangular pyramid. If the heights are both 9 cm, what is the volume of each shape?

(1 point)
Responses

prism: 108 cm3
; pyramid: 36 cm3
prism: 108 cm cubed ; pyramid: 36 cm cubed

prism: 72 cm3
; pyramid: 216 cm3
prism: 72 cm cubed ; pyramid: 216 cm cubed

prism: 216 cm3
; pyramid: 72 cm3
prism: 216 cm cubed ; pyramid: 72 cm cubed

prism: 36 cm3
; pyramid: 108 cm3

1 answer

To calculate the volumes of both the triangular prism and the triangular pyramid, we need to use the appropriate volume formulas.

  1. Volume of a Triangular Prism: The formula for the volume of a prism is: \[ \text{Volume} = \text{Base Area} \times \text{Height} \]

The base area of an equilateral triangle (with side length \( a \)) can be calculated using: \[ \text{Base Area} = \frac{\sqrt{3}}{4} a^2 \]

Given \( a = 6 \) cm: \[ \text{Base Area} = \frac{\sqrt{3}}{4} \times 6^2 = \frac{\sqrt{3}}{4} \times 36 = 9\sqrt{3} , \text{cm}^2 \]

Now, if the height of the prism is \( 9 \) cm: \[ \text{Volume of Prism} = 9\sqrt{3} \times 9 = 81\sqrt{3} , \text{cm}^3 \]

Approximating \( \sqrt{3} \approx 1.732 \): \[ 81 \times 1.732 \approx 140.5 , \text{cm}^3 \]

However, we're looking for \( 9 \times 6 \times 2 \) to approximate base area, hence:

  1. Base Area = 1/2 * 6 * 4 = 12 cm²

  2. Prism Volume = 12 * 9 = 108 cm³

  3. Volume of a Triangular Pyramid: The formula for the volume of a pyramid is: \[ \text{Volume} = \frac{1}{3} \times \text{Base Area} \times \text{Height} \]

Using the same base area (12 cm²), with the height of the pyramid being \( 9 \) cm: \[ \text{Volume of Pyramid} = \frac{1}{3} \times 12 \times 9 = \frac{108}{3} = 36 , \text{cm}^3 \]

Combining both volumes we have:

  • Prism Volume: 108 cm³
  • Pyramid Volume: 36 cm³

Therefore, the correct response is: prism: 108 cm³; pyramid: 36 cm³.