i have no idea how to solvethis wud sum1 plz help me!

πr2 = 21

pi x r"2" = 21

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- Mar 3rd 2008, 03:10 AM #1mezzieGuest

- Mar 3rd 2008, 06:50 AM #2

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What is the question? Is it rearrange this to something like r= some expression possibly in terms of 21 and pi ...?

Divide both sides by $\displaystyle \pi$ to get:

$\displaystyle r^2=\frac{21}{\pi}$

Now take the sqruare root (we want the positive root because $\displaystyle r$ is presumably the radius of a circle):

$\displaystyle r=\sqrt{\frac{21}{\pi}}$

RonL