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tunnel entrance..

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tunnel entrance..

by sairamGmat » Wed Aug 11, 2010 12:46 am
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) 9Ï€
(B) 12Ï€
(C) 9Ï€ * sqrt(2)
(D) 18Ï€
(E) 9Ï€ / sqrt(2)

OA is C
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by kvcpk » Wed Aug 11, 2010 1:13 am
sairamGmat wrote: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) 9Ï€
(B) 12Ï€
(C) 9Ï€ * sqrt(2)
(D) 18Ï€
(E) 9Ï€ / sqrt(2)

OA is C
Are you sure that the question is not missing soimething.
With only Chord length, many circles can be drawn.
"Once you start working on something,
don't be afraid of failure and don't abandon it.
People who work sincerely are the happiest."
Chanakya quotes (Indian politician, strategist and writer, 350 BC-275BC)
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by gmatmachoman » Wed Aug 11, 2010 9:52 pm
kvcpk wrote:
sairamGmat wrote: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) 9Ï€
(B) 12Ï€
(C) 9Ï€ * sqrt(2)
(D) 18Ï€
(E) 9Ï€ / sqrt(2)

OA is C
Are you sure that the question is not missing soimething.
With only Chord length, many circles can be drawn.

praveen bhai,
I think question is rite...I really tried a lot of combinations..but I would have easily picked C as we are sure perimeter will be less than 12 pi. So naturally I would have gone for C...

But i am really looking for a logical answer..
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by kvcpk » Wed Aug 11, 2010 10:07 pm
gmatmachoman wrote: praveen bhai,
I think question is rite...I really tried a lot of combinations..but I would have easily picked C as we are sure perimeter will be less than 12 pi. So naturally I would have gone for C...

But i am really looking for a logical answer..
Machoman Bhai,
Perimeter should be slightly greater than 12 pi. It cannot be less than 12 pi. Because, 12 is the chord lengtn.

I believe, there is some value missing in the picture.
"Once you start working on something,
don't be afraid of failure and don't abandon it.
People who work sincerely are the happiest."
Chanakya quotes (Indian politician, strategist and writer, 350 BC-275BC)
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by selango » Wed Aug 11, 2010 10:34 pm
Praveen,

One doubt here.If we take curved portion fully as a circle then base is diameter.

Perimeter(ie)Circumference=Pi*d=12*pi

So the curved portion ll be slightly less than 12Pi

Am I right?
--Anand--
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