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# m12 34

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Intern
Joined: 07 Oct 2011
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m12 34 [#permalink]  11 Jun 2012, 17:25
If the diameter of a compact disk is 14 cm and the diameter of the hole in the center of the disk is 2 cm, what is the area of the compact disk?

1) 48pi
2) 52pi
3) 76pi
4) 122pi
5) 140pi

Could someone please explain clearly, if possible with diagram?
Intern
Joined: 10 Mar 2012
Posts: 28
Location: India
GMAT Date: 11-30-2012
WE: Design (Manufacturing)
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Re: m12 34 [#permalink]  11 Jun 2012, 19:38
karthiksms wrote:
If the diameter of a compact disk is 14 cm and the diameter of the hole in the center of the disk is 2 cm, what is the area of the compact disk?

1) 48pi
2) 52pi
3) 76pi
4) 122pi
5) 140pi

Could someone please explain clearly, if possible with diagram?

Area of the compact disc would be the difference between the area of the disc minus the area of the hole:

Compact Disc:
Dia = 14cm / radius = 7cm
Area = Pi*7^2=49Pi

Hole:
Area = Pi*1^2=Pi

Hence area of the compact disc = 49Pi-Pi=48 Pi
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Joined: 01 May 2012
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Re: m12 34 [#permalink]  11 Jun 2012, 21:51
So if you want to know the area covered by the donut itself is

7*7*pi - 1*1*pi = 48 pi

http://www.millersamuel.com/files/2012/ ... ddonut.jpg
Re: m12 34   [#permalink] 11 Jun 2012, 21:51
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# m12 34

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