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Geometry GMAT Prep question- Experts plz confirm ans.

Problem Solving — algebra and arithmetic (GMAT Focus Edition)
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Geometry GMAT Prep question- Experts plz confirm ans.

by anks17 » Thu Aug 09, 2012 7:52 pm
GMAT Experts,

Shouldn't the answer for attached question be pi*S(2R + S)? Can you please confirm the same.Thanks.
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Geometry GMAT Prep question- Experts plz confirm answer ASAP
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by eagleeye » Thu Aug 09, 2012 8:05 pm
anks17 wrote:GMAT Experts,

Shouldn't the answer for attached question be pi*S(2R + S)? Can you please confirm the same.Thanks.
Radius of medallion = r
Radius of glass interior = r-s

Area = pi * (r^2 -(r-s)^2) = pi * ( (r+r-s)(r-r+s)) = pi * (2r-s)(s) . ( using a^2-b^2 = (a+b)(a-b) )

E is correct.
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by anks17 » Thu Aug 09, 2012 8:13 pm
I solved as below. What is wrong ?

Radius of Outer circle = R+S and Radious of Inner Circle = R
(as per diagram and question)

Area of Outer Circle = Pi * (R+S)^2
Area of Inner Circle - Pi * R^2
Area of Shaded Portion or Metal Frame = Pi [(R+S)^2 - (R^2)]= Pi(S^2 + 2S)
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by anks17 » Thu Aug 09, 2012 8:17 pm
Eagleeye, got it, It seems R is radius of Outer Circle and I thought that it is radius of inner circle and hence a different answer, Thanks for your quick replies
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