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A equilateral triangle question?

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A equilateral triangle question?

by jayhgmat » Sat Mar 12, 2011 6:36 pm
The following question is from GMATPrep.
A equilateral triangle is inscribed in a circle, the length of triangle is 24. what is the approximate diameter of the circle.

A. 5
B. 8
C. 11
D. 13
E. 15

Answer: C

Why????Why???Why not B???
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by Anurag@Gurome » Sat Mar 12, 2011 11:48 pm
jayhgmat wrote:A equilateral triangle is inscribed in a circle, the length of triangle is 24. what is the approximate diameter of the circle.

A. 5
B. 8
C. 11
D. 13
E. 15
In the actual GMATPrep problem, 24 is the length of the arc ABC, not the triangle.

Now, the measure of the angle subtended by the arc ABC at the center of the circle = 240 degrees

Therefore, perimeter of the circle = (24/240)*360 = 36

Hence, diameter of the circle = 36/pi = 36/3.14 ≈ 11

The correct answer is C.
Anurag Mairal, Ph.D., MBA
GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
1-800-566-4043 (USA)

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