Finding the area of a circle inscribed another circle

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May 23rd 2007, 05:20 PM
thumpin_termis

Finding the area of a circle inscribed another circle

So here's the question and the highlighted answer.
http://i118.photobucket.com/albums/o...medal_ques.jpg

Here's what I did to solve it, but I don't come up with the correct answer. What am I doing wrong here?
http://i118.photobucket.com/albums/o...medal_work.jpg
May 23rd 2007, 05:41 PM
Jhevon

Quote:

Originally Posted by thumpin_termis

So here's the question and the highlighted answer.
http://i118.photobucket.com/albums/o...medal_ques.jpg

Here's what I did to solve it, but I don't come up with the correct answer. What am I doing wrong here?
http://i118.photobucket.com/albums/o...medal_work.jpg

You misread the question, the medalian is the colored glass + the frame, so r is the outer radius and r - s is the inner radius. thus your equation should be:

$A = \pi r^2 - \pi (r - s)^2$
May 23rd 2007, 05:50 PM
thumpin_termis

Ah ha. I see. Now I get the correct answer. Thank you! :)