Quandaries and Queries


Kim 10th grader

a sphere has a surface area of 128 pi sq. units. What is its exact radius?
formula is 4 pi r2 I believe but how do I get radius



Hi Kim,

Since the surface area is given by 4 pi r2 and the value is 128 pi sq units you know that

4 pi r2 = 128 pi. If you divide both sides by 4 pi you get r2 = 32, and thus r is the square root of 32 which is 4 times the root of 2.


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