SAT Math : How to find the surface area of a pyramid

Study concepts, example questions & explanations for SAT Math

varsity tutors app store varsity tutors android store varsity tutors ibooks store

Example Questions

Example Question #741 : Geometry

The Pyramid of Giza has a height of 480 feet. If the length of each side of the base is approximately 756 feet, what is its total surface area? Round to the nearest tenth.

Possible Answers:

\(\displaystyle 1,495,368 ft^{2}\)

\(\displaystyle 752,976 ft^{2}\)

\(\displaystyle 802,494 ft^{2}\)

\(\displaystyle 934,416 ft^{2}\)

Correct answer:

\(\displaystyle 1,495,368 ft^{2}\)

Explanation:

If the length of one side is 756 ft, then multiply to find the area of the base.

\(\displaystyle \text{Area of square} = \text{length} \times \text{width}\)

\(\displaystyle A=756\times756\)

\(\displaystyle A=571,536 ft^{2}\)

Once you've found the area of the base, use the height of the pyramid and half of the side length of the base to determine the length of the side from the apex to the ground using the Pythagorean Theorem. 

\(\displaystyle 480^{2}+378^{2}=c^{2}\)

\(\displaystyle 230,400+142,884=c^{2}\)

\(\displaystyle 373,284=c^{2}\)

\(\displaystyle 611=c\)

Using the side length of the base and the height of each of the triangles that form the pyramid, calculate the area of each triangle, then multiply by 4.

\(\displaystyle \text{Area of a triangle}=\frac{1}{2}\times \text{base} \times \text{height}\)

\(\displaystyle A=\frac{1}{2} \times 611 \times 756\)

\(\displaystyle A=230,958\)

\(\displaystyle \text{Area of four triangles} = 4 \times 230,958\)

\(\displaystyle A=923,832 ft^{2}\)

Add the surface area of the base to the surface area of the four triangles.

\(\displaystyle \text{Total surface area} = 571,536 + 923,832\)

\(\displaystyle 1,495,368 ft^{2}\)

Learning Tools by Varsity Tutors