Pearson Geometry Common Core, 2011
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Pearson Geometry Common Core, 2011 View details
3. Surface Areas of Pyramids and Cones
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Exercise 11 Page 713

Use the formula for the surface area of a pyramid.

179 in.^2

Practice makes perfect

We want to find the surface area of the given pyramid.

To calculate the surface area of a pyramid, we can use the formula where p is the perimeter of the base, l is the slant height, and B is the area of the base. S.A.=1/2pl+B The base of the pyramid is a square with the side length of 8 inches. Let's calculate its perimeter! p=4s ⇒ p=4( 8)=32in. The area of the square equals the squared length of the side. B=s^2 ⇒ B= 8^2=64in.^2 We are also given that the slant height l is 7.2 inches. Let's substitute all of these values into the formula for the surface area and calculate it.
S.A.=1/2pl+B
S.A.=1/2(32)(7.2)+64
Simplify right-hand side
S.A.=230.4/2+64
S.A.=115.2+64
S.A.=179.2
S.A.≈ 179
The surface area of the pyramid is about 179 square inches.