SOLUTION: What is the approximate area of a circle with a circumfrence of 15 in.?

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Question 848646: What is the approximate area of a circle with a circumfrence of 15 in.?
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
What is the approximate area of a circle with a circumference of 15 in.?
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First use the circumference to find the radius


C+=+2%2Api%2Ar


15+=+2%2Api%2Ar


15%2F%282%2Api%29+=+r


r+=+15%2F%282%2Api%29 ... I'll leave it in its exact form.


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Now use this radius to find the area


A+=+pi%2Ar%5E2


A+=+pi%2A%2815%2F%282%2Api%29%29%5E2


A+=+pi%2A%28225%2F%284%2Api%5E2%29%29


A+=+%28225pi%29%2F%284%2Api%5E2%29


A+=+%28225%29%2F%284pi%29 <--- This is the exact area in terms of pi


A+=+17.9049310978382 <--- This is the approximate area, which is the final answer* they want.


Notes:

* Be sure to follow any rounding rules given (eg: "round to the nearest hundredth")

* Much of this problem can be done without a calculator, but you will need a calculator for that last step (to get the approximate answer).

* The units of the final answer are "square inches"