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Circumference and Diameter

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Circumference and Diameter

by GmatKiss » Sun May 20, 2012 3:50 am
If k : 3 is the ratio of the circumference to the diameter of a circle with radius x, then what is the ratio of the circumference to the diameter of a circle with radius 2x?

k:3
k:6
2k:3
2k:6
4k:6
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by ankita1709 » Sun May 20, 2012 4:14 am
I guess the answers should be [spoiler]k:3 i.e. A[/spoiler]

Reason being:
Circumference/Dia = 2*pi*r/2*r =>pi

Hence it should not matter what the radius is
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by ihatemaths » Sun May 20, 2012 4:46 am
k:3
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by Anurag@Gurome » Sun May 20, 2012 8:14 am
GmatKiss wrote:If k : 3 is the ratio of the circumference to the diameter of a circle with radius x, then what is the ratio of the circumference to the diameter of a circle with radius 2x?

k:3
k:6
2k:3
2k:6
4k:6
Explanation in detail:

Circumference of the circle = 2(pi)x
Diameter of circle = 2x
Circumference : Diameter = 2(pi)x : 2x = pi : 1
So, pi : 1 = k : 3

When radius of circle = 2x, its circumference = 2(pi) * 2x = 4(pi)x and diameter = 2 * (2x) = 4x
Circumference : Diameter = 4(pi)x : 4x = pi : 1 = [spoiler]k : 3[/spoiler]

The correct answer is A.
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