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# The figure shows the top side of a circular medallion made

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SVP
Joined: 21 Jul 2006
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The figure shows the top side of a circular medallion made [#permalink]  25 Jan 2008, 03:17
00:00

Difficulty:

25% (low)

Question Stats:

70% (02:41) correct 29% (01:37) wrong based on 58 sessions
Attachment:
File comment: Circle

Circle.JPG [ 19.94 KiB | Viewed 1587 times ]
The figure shows the top side of a circular medallion made of a circular piece of colored glass surrounded by a metal frame, represented by the shaded region. If the redius 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) pi*s(2r-s)

OPEN DISCUSSION OF THIS QUESTION IS HERE: the-figure-shows-the-top-side-of-a-circular-medallion-made-o-101845.html
[Reveal] Spoiler: OA
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CEO
Joined: 17 Nov 2007
Posts: 3599
Concentration: Entrepreneurship, Other
Schools: Chicago (Booth) - Class of 2011
GMAT 1: 750 Q50 V40
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Kudos [?]: 1574 [0], given: 354

Re: PS Geometry: Circles [#permalink]  25 Jan 2008, 03:21
Expert's post
B

Area=\pi r^2-\pi s^2=\pi (r^2-s^2)
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SVP
Joined: 21 Jul 2006
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Re: PS Geometry: Circles [#permalink]  25 Jan 2008, 03:52
wrong choice. This is a gmatprep question. The OA is E. But how and why?
CEO
Joined: 17 Nov 2007
Posts: 3599
Concentration: Entrepreneurship, Other
Schools: Chicago (Booth) - Class of 2011
GMAT 1: 750 Q50 V40
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Kudos [?]: 1574 [0], given: 354

Re: PS Geometry: Circles [#permalink]  25 Jan 2008, 04:00
Expert's post
E stupid mistake

Area=\pi r^2-\pi (r-s)^2=\pi (r^2-r^2-s^2+2rs)=\pi s(2r-s)
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Director
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Re: PS Geometry: Circles [#permalink]  25 Jan 2008, 08:25
thanks for the question. But please put GMATPrep in the subject line if it is a GMATPrep question (since many people like myself want to save these for exam conditions).

cheers,
Director
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Re: The figure shows the top side of a circular medallion made [#permalink]  08 Mar 2013, 05:12
I didn't understand pi ( R - s)^2 could someone explain this?
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Re: The figure shows the top side of a circular medallion made [#permalink]  08 Mar 2013, 05:17
Expert's post
fozzzy wrote:
I didn't understand pi ( R - s)^2 could someone explain this?

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Re: The figure shows the top side of a circular medallion made   [#permalink] 08 Mar 2013, 05:17
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