# Re: Area and circumference of a circle

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Posted by Denis Borris on September 28, 2002 at 22:27:38:

In Reply to: Re: Area and circumference of a circle posted by Derringer on September 28, 2002 at 18:28:04:

: : : How do I find the area of a circle with a circumference of 100 pi? How do I find the circumference if the area is 100 pi?
: : : All I have for information is that the area of a circle is A=(pi) (r^2) and that the circumference is is C=(2pi)(r)
: : Solve for r then plug it into the other equation.
: : What is the radius of a circle with circumference of 100 pi?
: : Then with that answer find the Area.
: So, would that look like:
: r=2pi divided by 100pi?

Gee, you ain't too fast on the draw, Derringer!

if circumference is 100(pi), then 2r(pi) = 100(pi)
so 2r = 100 : divide each side by (pi)
r = 50
....now you figure out area!

if area is 100(pi), then (pi)r^2 = 100(pi)
so r^2 = 100 : divide each side by (pi)
r = 10
...now you figure out the circumference!

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