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# What is the ratio of the circumference of the outer circle to that of

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Math Expert
Joined: 02 Sep 2009
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What is the ratio of the circumference of the outer circle to that of  [#permalink]

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30 Aug 2018, 04:53
00:00

Difficulty:

35% (medium)

Question Stats:

74% (00:40) correct 26% (00:50) wrong based on 25 sessions

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What is the ratio of the circumference of the outer circle to that of the inner circle?

(1) The area of the outer circle is 4 times the area of the inner circle.
(2) The circles share the same center.

Attachment:

image001.gif [ 587 Bytes | Viewed 556 times ]

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What is the ratio of the circumference of the outer circle to that of  [#permalink]

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30 Aug 2018, 06:50
Let R be the radius of the outer circle.

Let r be the radius of the smaller circle.

From statement 1:

Given Pi*$$R^2$$ = 4*Pi*$$r^2$$

Then $$(\frac{R}{r})^2$$ = 4

$$\frac{R}{r}$$ = 2

Circumference = $$\frac{2*Pi*R}{2*Pi*r}$$ = $$\frac{R}{r}$$ = 2.

Ratio becomes 2:1

1 is sufficient.

From statement 2:

Insufficient.

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Re: What is the ratio of the circumference of the outer circle to that of  [#permalink]

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30 Aug 2018, 07:05
1
Bunuel wrote:

What is the ratio of the circumference of the outer circle to that of the inner circle?

(1) The area of the outer circle is 4 times the area of the inner circle.
(2) The circles share the same center.

Attachment:
image001.gif

Question stem:- What is the ratio of the circumference of the outer circle to that of the inner circle?

St1:-The area of the outer circle is 4 times the area of the inner circle.
Here, relationship between radii is given.
Sufficient.

St2:- The circles share the same center.
Neither of the required info is given,
Insufficient.

Ans. (A)
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Re: What is the ratio of the circumference of the outer circle to that of   [#permalink] 30 Aug 2018, 07:05
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