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# The circumference of circle C

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The circumference of circle C [#permalink]  18 Mar 2018, 10:15
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Question Stats:

76% (00:27) correct 23% (00:00) wrong based on 13 sessions
The circumference of circle C is $$18\pi$$

 Quantity A Quantity B The diameter of circle C 9

A) Quantity A is greater.
B) Quantity B is greater.
C) The two quantities are equal.
D) The relationship cannot be determined from the information given.
[Reveal] Spoiler: OA

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Re: The circumference of circle C [#permalink]  02 Apr 2018, 19:35
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The formula for the circumference of a circle is mandatory stuff: it's πD (or π times the diameter). We've been told the circumference is 18π, so the diameter must be 18. Thus, A is the answer.

(Side note: the testmakers are hoping you get the diameter and the radius mixed up here. It's not intellectually challenging to distinguish between the two, but it's an easy mistake to make no matter how good you are at math, so always be careful with radii and diameters. My recommendation is that you never deal with diameters, and if you're given a diameter, always just change it to a radius. You're less likely to accidentally use one in place of the other this way. But in this particular problem, I broke my own rule because they literally gave us the diameter and asked for it so it seems foolish to convert it to a radius and back again.)
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Re: The circumference of circle C   [#permalink] 02 Apr 2018, 19:35
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# The circumference of circle C

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