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# This probably is confusing to me. The figure shows the top

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Intern
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This probably is confusing to me. The figure shows the top [#permalink]  31 Dec 2005, 14:04
This probably is confusing to me.

The figure shows the top side of a circular medallion made of a circular piece of colored glass surrounded by a metal fram, represented by the shaded region. If the radius of the medallion is r centimeters and the width of the metal frame is s centimeters, then in terms of s and r, what is the area of the metal frame in square centimeters?

a. pi(r-s)^2
b. pi(r^2-s^2)
c. 2pi(r-s)
d. pir(2r-s)
e. pis(2r-s)

Can someone please explain to me how they arrive to the answer? Thanks for your help!
Director
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[#permalink]  31 Dec 2005, 16:00
Can you please provide the figure?
Intern
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[#permalink]  31 Dec 2005, 16:51
Attached is what the figure looks like. Thanks!
Attachments

Doc1.doc [23.5 KiB]

Director
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[#permalink]  01 Jan 2006, 01:51
The area of the entire medallion is r^2 *PI, the non-metal area (r-s)^2 *PI

Substract the smaller part from the entire: r^2 * PI - (r-s)^2 *PI

= PIs(2r-s)
Manager
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[#permalink]  03 May 2006, 13:26
Hi-
I got this on the gmatprep, OA is pi*s(2r-s), and my answer is pi*s(2r+s).

shouldn;t the area of the larger part (medaillion+frame) = Pi*(r+s)^2
and the medallion itself is pi*r^2
so the area of the frame is
pi*(r+s)^2 - pi*r^2 = pi*r^2 + 2*pi*rs + pi*s^2 - pi*r^2
which the pi*r^2 terms cancel out, facot out pi and s and you have
pi*s(2r+s)
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[#permalink]  03 May 2006, 14:29
Agreed it shud be pi*s(s+2r)

Eessentially, its
pi*((r+s)^2) - pi*(r^2)
Manager
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[#permalink]  03 May 2006, 18:52
If we're right, that's the 2nd error i've spotted in GMATPrep

Manager
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[#permalink]  04 May 2006, 05:33
I get PI*s*(2r+s) as well
Director
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[#permalink]  04 May 2006, 06:17
i too got piS(2r + s)
Hope the real gmat doesnt have these errors
Intern
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[#permalink]  04 May 2006, 06:32
I agree even I get 2pis(2r+s)
Manager
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[#permalink]  04 May 2006, 06:46
Agreed. There is some ambiguity in the question. That is, does the radius r represent the medallion's radius that also includes the width of the frame S or is the radius r only for the face and the width S is seperate?
When I first had a crack at it, my answer was pis(2r+s) but when I included the width of S to be part of r, the answer changed to pis(2r-s).
Manager
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[#permalink]  04 May 2006, 07:40
Agreed. There is some ambiguity in the question. That is, does the radius r represent the medallion's radius that also includes the width of the frame S or is the radius r only for the face and the width S is seperate?
When I first had a crack at it, my answer was pis(2r+s) but when I included the width of S to be part of r, the answer changed to pis(2r-s).

true. but from the wording, it clearly says "a medallion surrounded by a metal frame...the radius of the medallion is r and the width of the frame is s"

it's either an error, or a horribly inspecific question if that was the intent.
[#permalink] 04 May 2006, 07:40
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# This probably is confusing to me. The figure shows the top

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