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# If the ratio of the circumference of a circle to the area of the same

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Joined: 02 Sep 2009
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If the ratio of the circumference of a circle to the area of the same  [#permalink]

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27 Apr 2017, 02:42
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Question Stats:

73% (00:48) correct 27% (00:34) wrong based on 107 sessions

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If the ratio of the circumference of a circle to the area of the same circle is 1 to 3, what is the diameter of the circle?

A. 2
B 3
C. 6
D. 12
E. 18

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Re: If the ratio of the circumference of a circle to the area of the same  [#permalink]

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27 Apr 2017, 02:45
Let the radius of the cicle be R
2*pi*R / pi*R*R = 1/3
2/R = 1/3
R = 6
Diameter = 2R = 12(Option D)
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Re: If the ratio of the circumference of a circle to the area of the same  [#permalink]

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30 Apr 2017, 08:53
I worked backwards by using the answer choices. If we plug in answer choice D:

d=12, then radius = 6 and circumference = 12pi.

now, we can find the area.

A= piR^2 = pi6^2 = 36pi.

circumference: area = 12pi: 36pi reduce this and we get the stated ratio of 1:3
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Re: If the ratio of the circumference of a circle to the area of the same  [#permalink]

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30 Apr 2017, 11:05
1
Bunuel wrote:
If the ratio of the circumference of a circle to the area of the same circle is 1 to 3, what is the diameter of the circle?

A. 2
B 3
C. 6
D. 12
E. 18

Solution

• We need to find the Diameter of the circle $$= D$$ (assumed)

o The circumference of the circle is given by $$= 2π*(\frac{D}{2}) = πD$$

o Area of the circle $$= π*\frac{D^2}{4}$$

• We are given

o $$\frac{Area}{Circumference}= \frac{3}{1}$$

o $$\frac{(πD^2)}{(4πD)} = \frac{3}{1}$$

o D = 12

• Hence the correct answer is Option D

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Saquib
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Re: If the ratio of the circumference of a circle to the area of the same  [#permalink]

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06 May 2017, 17:29
Bunuel wrote:
If the ratio of the circumference of a circle to the area of the same circle is 1 to 3, what is the diameter of the circle?

A. 2
B 3
C. 6
D. 12
E. 18

We can let r = the radius of the circle and create the following equation:

2πr/πr^2 = 1/3

6πr = πr^2

6r = r^2

6 = r

Thus, the diameter is 2 x 6 = 12.

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Re: If the ratio of the circumference of a circle to the area of the same  [#permalink]

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18 May 2017, 04:09
given = 2(pi)r / (pi) r^2 = 1/3 solving for r => r = 6 hence diameter is 2r = 12

Option D is correct
Re: If the ratio of the circumference of a circle to the area of the same &nbs [#permalink] 18 May 2017, 04:09
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