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# What is the difference in the circumferences of circles A and B?

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Math Expert
Joined: 02 Sep 2009
Posts: 50572
What is the difference in the circumferences of circles A and B?  [#permalink]

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11 Sep 2018, 02:07
00:00

Difficulty:

45% (medium)

Question Stats:

78% (00:42) correct 22% (01:48) wrong based on 9 sessions

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What is the difference in the circumferences of circles A and B?

(1) The difference in the areas of the two circles is 4.
(2) The difference in radii of the two circles is 2.

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Re: What is the difference in the circumferences of circles A and B?  [#permalink]

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11 Sep 2018, 03:30
Bunuel wrote:
What is the difference in the circumferences of circles A and B?

(1) The difference in the areas of the two circles is 4.
(2) The difference in radii of the two circles is 2.

Question: What is the difference in the circumferences of circles A and B = $$2π(r_1 - r_2)$$ = ?

Statement 1: The difference in the areas of the two circles is 4

i.e. $$π(r_1^2 - r_2^2) =4$$
i.e. $$π(r_1-r_2)*(r_1+r_2) = 4$$
But we dont have $$(r_1+r_2)$$ hence

NOT SUFFICIENT

Statement 2: he difference in radii of the two circles is 2

So, difference in the circumferences of circles A and B = $$2π(r_1 - r_2) = 2π*2 = 4π$$

SUFFICIENT

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Re: What is the difference in the circumferences of circles A and B? &nbs [#permalink] 11 Sep 2018, 03:30
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