find circumference of circle, given area

dede

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Sep 28, 2006
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What is the circumference in meters of a circle whose area is 100 pi square meters?
 
Re: cir of circle

Hello, Dede!

dede said:
What is the circumference in meters of a circle whose area is 100 pi square meters?

Lets start off with what we know:


\(\displaystyle \L \;100 \pi\,=\,\pi r^2\)


\(\displaystyle \L \;100\,=\,r^2\)


\(\displaystyle \L \;10\,=\,r\)


Circumference is:\(\displaystyle \L \;C\,=\,\pi d\)

\(\displaystyle d\,=\,diameter\)


So the circumference is:\(\displaystyle \L \;20\pi\,m\)
 
jonboy, check your 1st equation; should be 100 = pi r^2
 
Denis said:
jonboy, check your 1st equation; should be 100 = pi r^2
But didn't the exercise say that the "area is 100 pi square meters"? Why would the area expression be "100" instead of "100 pi"...?

Thank you.

Eliz.
 
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