A rectangular pyramid has a base with sides 14 ft. and 13 ft. The slant height where the base has the longer side is 12 ft., and the slant height where the base has the shorter side is 13 ft. Which of the following correctly calculates the lateral surface area of the pyramid?

1 answer

To calculate the lateral surface area of a rectangular pyramid, we need to find the area of the four triangular faces that make up the sides of the pyramid.

The formula for the lateral surface area \( A_L \) of a pyramid is given by the sum of the areas of the triangular sides. For a rectangular pyramid, we can separate the faces based on the dimensions of the base.

  1. Identify the Dimensions:

    • Base length (\( b_1 \)): 14 ft
    • Base width (\( b_2 \)): 13 ft
    • Slant height corresponding to base length (\( l_1 \)): 12 ft
    • Slant height corresponding to base width (\( l_2 \)): 13 ft
  2. Calculate Areas of the Triangular Faces:

    • Two triangular faces correspond to the longer side (base length of 14 ft):

      • Area of one triangular face: \[ A_{triang1} = \frac{1}{2} \times b_1 \times l_1 = \frac{1}{2} \times 14 \times 12 = 84 \text{ ft}^2 \]
      • So, total area for the two triangular faces corresponding to the longer side: \[ A_{triang1, total} = 2 \times 84 = 168 \text{ ft}^2 \]
    • Two triangular faces correspond to the shorter side (base width of 13 ft):

      • Area of one triangular face: \[ A_{triang2} = \frac{1}{2} \times b_2 \times l_2 = \frac{1}{2} \times 13 \times 13 = \frac{169}{2} = 84.5 \text{ ft}^2 \]
      • So, total area for the two triangular faces corresponding to the shorter side: \[ A_{triang2, total} = 2 \times 84.5 = 169 \text{ ft}^2 \]
  3. Calculate the Total Lateral Surface Area: Combine the areas of all four triangular faces: \[ A_L = A_{triang1, total} + A_{triang2, total} = 168 + 169 = 337 \text{ ft}^2 \]

Thus, the lateral surface area of the pyramid is \( \mathbf{337 \text{ ft}^2} \).