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# The circumference of circle C1 is 12π and the circumference of circle

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Math Expert
Joined: 02 Sep 2009
Posts: 55150
The circumference of circle C1 is 12π and the circumference of circle  [#permalink]

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27 Nov 2018, 00:02
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00:00

Difficulty:

15% (low)

Question Stats:

91% (01:09) correct 9% (01:30) wrong based on 28 sessions

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The circumference of circle C1 is 12π and the circumference of circle C2 is 24π. What is the ratio of the area of C2 to the area of C1 ?

A. 2 to 1
B. 3 to 1
C. 4 to 1
D. 6 to 1
E. 8 to 1

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Joined: 18 Jul 2018
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Location: India
Concentration: Finance, Marketing
WE: Engineering (Energy and Utilities)
Re: The circumference of circle C1 is 12π and the circumference of circle  [#permalink]

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28 Nov 2018, 01:14
1
Circumference C1 = 12π = 2πr, then r = 6.
Circumference C2 = 24π = 2πr, then r = 12.

$$\frac{Area of C_2}{Area of C_1}$$ = $$\frac{πr_2^2}{πr_1^2}$$ = $$\frac{12*12}{6*6}$$ = 4/1

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Re: The circumference of circle C1 is 12π and the circumference of circle   [#permalink] 28 Nov 2018, 01:14
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