SOLUTION: The radius of a circle was increased by 25 percent. By what percent did the area of the circle increase?

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Question 834817: The radius of a circle was increased by 25 percent. By what percent did the area of the circle increase?
Answer by reviewermath(1029) About Me  (Show Source):
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Q:
The radius of a circle was increased by 25 percent. By what percent did the area of the circle increase?
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Answer:
Area of Circle, A = pi%2Ar%5E2
If old radius, r%5Bold%5D = 1, then new radius, r%5Bnew%5D = 1.25 and
percent increase = %28pi%2A%281.25%5E2%29+-+pi%2A%281%5E2%29%29%2F%28pi%2A%281%5E2%29%29, divide the numerator and denominator by pi
percent increase = %281.25%5E2-+1%5E2%29%2F1%5E2 = 0.5625 or 56.25%