(Surface Area of Rectangular Prisms and Pyramids MC)

A net of a rectangular pyramid is shown in the figure.

A net of a triangular prism with base dimensions of 7 inches by 9 inches. The larger triangular face has a height of 8 inches. The smaller triangular face has a height of 8.5 inches.

What is the surface area of the pyramid?

97.25 in2
131.5 in2
194.5 in2
257.5 in2

1 answer

To find the surface area of a rectangular pyramid, we need to determine the area of the base and the area of the four triangular faces.

Step 1: Calculate the area of the base

Given that the base is a rectangle, we need its dimensions. However, those dimensions are not provided. For the sake of this problem, let's assume the base dimensions are \( b \) (length) and \( w \) (width).

The area \( A_{base} \) of the rectangular base is: \[ A_{base} = b \times w \]

Step 2: Calculate the area of the triangular faces

A rectangular pyramid has four triangular faces.

  • The area of each triangular face is given by the formula: \[ A_{triangle} = \frac{1}{2} \times \text{base} \times \text{height} \]
  • For a rectangular pyramid, each triangular face uses one dimension from the base of the pyramid and the height from the apex of the pyramid down to the base.

Assuming example dimensions for calculation:

Let's assume:

  • Base dimensions \( b = 9 \) inches and \( w = 7 \) inches.
  • Assuming the height of the pyramid is \( h \) inches.

Base area:

\[ A_{base} = 9 \times 7 = 63 , \text{in}^2 \]

Assuming triangular faces:

Assuming each triangular face uses the dimensions with respective height for the triangular faces. We will not use specific heights without knowing the configuration correctly, but let's just assign:

  • Height from apex to the base is about half of the base area height.

Let's say the height corresponding to the triangular face is 8 inches for one side, and the other triangular face is 8.5 inches.

Total area of the triangular sections: (not a precise answer without specific face base but for this area calculation)

For the calculations:

  • Larger triangular face area (using a base of 7 inches): \[ A_{triangle1} = \frac{1}{2} \times 7 \times 8 = 28 , \text{in}^2 \]

  • Smaller triangular face area (using a base of 9 inches): \[ A_{triangle2} = \frac{1}{2} \times 9 \times 8.5 = 38.25 , \text{in}^2 \]

Total area of triangular sections:

We will duplicate two of the triangular faces: \[ A_{triangular faces} = 2 \times (A_{triangle1} + A_{triangle2}) = 2 \times (28 + 38.25) = 2 \times 66.25 = 132.5 , \text{in}^2 \]

Combine to find surface area:

Add base and side areas together: \[ \text{Total Surface Area} = A_{base} + A_{triangular faces} = 63 + 132.5 = 195.5 \text{ in}^2 \]

However, since your options do not display this outcome, it seems each of these depends on a different base or heights that were assumed incorrectly.

Conclusion:

We might have not captured your exact base or heights correctly. Based on estimation and choosing values, the options should total from better accurately given values and depending also on possible rounding or misconnection in the pyramid type.

Given the understanding of your options and major estimations, the closest answer based on approximations using dimensions that fit real scenarios would lead to a total approximately to nearby options, thus:

194.5 in² (if better averaged).

So please adjust depending on how concrete your dimensions are in the triangular face arrangements.