College

A concrete monument in the shape of a regular pyramid with a square base weighs 13,400 pounds. The monument is 7.30 feet high. Compute the length of a base side. Assume that concrete weighs 137 pounds per cubic foot.

Answer :

To solve the problem of finding the side length of the square base of the concrete monument, let's follow these steps:

1. Determine the Volume of the Pyramid:
The weight of the concrete monument is 13,400 pounds. We know that concrete weighs 137 pounds per cubic foot. To find the volume of the pyramid, we use the formula:

[tex]\[
\text{Volume} = \frac{\text{Weight}}{\text{Weight per cubic foot}} = \frac{13400 \text{ pounds}}{137 \text{ pounds per cubic foot}}
\][/tex]

This gives us a volume of approximately 97.81 cubic feet.

2. Use the Formula for the Volume of a Pyramid:
The volume [tex]\(V\)[/tex] of a pyramid with a square base can be calculated using the formula:

[tex]\[
V = \frac{1}{3} \times \text{Base Area} \times \text{Height}
\][/tex]

We already know the volume is about 97.81 cubic feet, and the height of the pyramid is 7.30 feet. Plugging in these values, we get:

[tex]\[
97.81 = \frac{1}{3} \times \text{Base Area} \times 7.30
\][/tex]

3. Solve for the Base Area:
To find the base area, rearrange the equation:

[tex]\[
\text{Base Area} = \frac{3 \times 97.81}{7.30}
\][/tex]

Calculating this gives us a base area of approximately 40.20 square feet.

4. Calculate the Side Length of the Base:
Since the base is a square, the side length [tex]\(s\)[/tex] can be found by taking the square root of the base area:

[tex]\[
s = \sqrt{\text{Base Area}} = \sqrt{40.20}
\][/tex]

This results in a side length of approximately 6.34 feet.

Thus, the length of a base side of the pyramid is approximately 6.34 feet.