Surface area of a sphere

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	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. Penny
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