GRE Math : How to find the surface area of a sphere

Study concepts, example questions & explanations for GRE Math

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Example Questions

Example Question #1 : Spheres

Find the surface area of a sphere with a diameter of 14. Use π = 22/7.

Possible Answers:






Correct answer:



Surface Area = 4πr2 = 4 * 22/7 * 72 = 616

Example Question #2 : Spheres

A sphere has a surface area of square inches.  If the radius is doubled, what is the surface area of the larger sphere?

Possible Answers:

Cannot be determined

Correct answer:


The surface area of the larger sphere is NOT merely doubled from the smaller sphere, so we cannot double to find the answer.

We can use the surface area formula to find the radius of the original sphere.

r2 = 4

r = 2

Therefore the larger sphere has a radius of 2 * 2 = 4.

The new surface area is then  square inches.

Example Question #3 : Spheres

If a sphere has a volume of  cubic inches, what is its surface area?

Possible Answers:






Correct answer:



The volume of a cube is equal to .

So we mutiply our volume by  and divide by , giving us .

The surface area of a sphere is equal to , giving us .

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