SOLUTION: How do you solve for the area of a shaded region? I have an unshaded circle within a shaded circle. The formula I was given is pi r squared. The numbers given are in the two circle

Algebra ->  Surface-area -> SOLUTION: How do you solve for the area of a shaded region? I have an unshaded circle within a shaded circle. The formula I was given is pi r squared. The numbers given are in the two circle      Log On


   

Question 424940: How do you solve for the area of a shaded region? I have an unshaded circle within a shaded circle. The formula I was given is pi r squared. The numbers given are in the two circles inside the shaded region each have a diameter of 3 and the shaded region is twelve. I tried squaring them and then subtracting. (it says to subtract the shaded region)
Answer by stanbon(75887) About Me  (Show Source):
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How do you solve for the area of a shaded region? I have an unshaded circle within a shaded circle. The formula I was given is pi r squared. The numbers given are in the two circles inside the shaded region each have a diameter of 3 and the shaded region is twelve. I tried squaring them and then subtracting. (it says to subtract the shaded region)
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Find the area of the larger circle.
A = pi*12^2 = 144pi
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Find the area of the inner circle.
a = pi*3^2 = 9pi
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Subtract the inner circle area from the larger circil area
to find the shaded area.
Area = 144pi-9pi = 135pi sq units.
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Cheers,
Stan H.
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