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# tunnel entrance

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Director
Joined: 25 Oct 2008
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Location: Kolkata,India

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21 Jun 2009, 03:45
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Question Stats:

100% (01:56) correct 0% (00:00) wrong based on 1 sessions

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This topic is locked. If you want to discuss this question please re-post it in the respective forum.

The figure above shows the shape of a tunnel entrance. If the curved portion is of a circle and the base of the entrance is 12 feet across, what is the perimeter, in feet, of the curved portion of the entrance'?

(A) 9π

(B) 12π

(C) 9 pie root2

(D) 18π

(E) 9 pie/root2
Attachments

gmat+ ps23(20).doc [23.5 KiB]

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http://gmatclub.com/forum/countdown-beginshas-ended-85483-40.html#p649902

Kudos [?]: 1137 [0], given: 100

Director
Joined: 03 Jun 2009
Posts: 782

Kudos [?]: 902 [0], given: 56

Location: New Delhi
WE 1: 5.5 yrs in IT

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22 Jun 2009, 02:14
Its just like, we have been provided with the length of chord and have been asked to find circumference of the circle. I think, there is something missing in this query
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Manager
Joined: 30 Nov 2008
Posts: 91

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22 Jun 2009, 14:53
If you say that the base forms a right angle with the center of the circle, you can use pythagoreans theorm and get x^2 + x^2 = 12^2 - and from this you can get r=6 root of 2. Using c=2 pi r you can assume that the triangle takes up i/4 of the circle and multiply the circumference times 3/4 you get 9 pi root of 2 as the answer. This is assuming a lot from this problem, it needs to tell more.

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Intern
Joined: 04 Mar 2008
Posts: 42

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22 Jun 2009, 15:04
benpack03 wrote:
If you say that the base forms a right angle with the center of the circle, you can use pythagoreans theorm and get x^2 + x^2 = 12^2 - and from this you can get r=6 root of 2. Using c=2 pi r you can assume that the triangle takes up i/4 of the circle and multiply the circumference times 3/4 you get 9 pi root of 2 as the answer. This is assuming a lot from this problem, it needs to tell more.

Kudos [?]: 3 [0], given: 6

Director
Joined: 03 Jun 2009
Posts: 782

Kudos [?]: 902 [0], given: 56

Location: New Delhi
WE 1: 5.5 yrs in IT

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22 Jun 2009, 21:50
I just searched on the net, and the correct problem is something like this

Quote:
The figure above shows the shape of a tunnel entrance. If the curved portion is 3/4 of a circle and the base of the entrance is 12 feet across, what is the perimeter, in feet, of the curved portion of the entrance'?

so, you know, this 3/4 was missing in the actual question.
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Re: tunnel entrance   [#permalink] 22 Jun 2009, 21:50
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