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# A certain singer at an outdoor concert can be heard for 1 mile...

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Intern
Joined: 20 May 2014
Posts: 12
A certain singer at an outdoor concert can be heard for 1 mile...  [#permalink]

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08 May 2015, 16:38
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Difficulty:

5% (low)

Question Stats:

87% (00:59) correct 13% (01:14) wrong based on 48 sessions

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A certain singer at an outdoor concert can be heard for 1 mile in all directions. after an adjustment is made to her microphone, the singer can be heard for 2 miles in all directions. by approximately how many square miles was the region in which should could be hard increased by the adjustment?

A. 1 square mile
B. π sq. miles
c. 2π sq. miles
D.3π sq. miles
E. 4π sq. miles
GMAT Tutor
Joined: 24 Jun 2008
Posts: 1881
Re: A certain singer at an outdoor concert can be heard for 1 mile...  [#permalink]

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08 May 2015, 16:51
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If anyone within 1 mile of the singer can hear her, that means there is a circle centered at the singer of radius 1 mile, and anyone within that circle can hear the singer. The area of that circle is π r^2 = π (1)^2 = π

After the microphone is adjusted, there is a circle of radius 2 miles around the singer, and anyone within that circle can hear her. The area of this new circle is π r^2 = π (2)^2 = 4π

The increase in area is just found by subtracting: 4π - π = 3π
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Re: A certain singer at an outdoor concert can be heard for 1 mile...   [#permalink] 08 May 2015, 16:51
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