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tangent circles

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by GMATinsight » Sun Aug 03, 2014 12:42 am
Answer : Option E

The distance between their centers could be 8 (r1+r2) or 2(r1-r2) even after combining the two statements


Since they are tangent therefore there is only one point of intersection the distance between their centers will be r1+r2 or r1-r2 (Internally tangent

But in case two points of intersection the distance between their center will be less than r1+r2 and greater than r1-r2

Also in case NO point of intersection the distance between their center will be greater than r1+r2 or lesser than r1-r2
Last edited by GMATinsight on Mon Aug 04, 2014 5:57 am, edited 1 time in total.
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by alexandrabiorka » Sun Aug 03, 2014 5:00 am
Thank you! There must have been an error in the answer choices in my book.
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by Matt@VeritasPrep » Sun Aug 03, 2014 5:34 pm
The answer is NOT C, unfortunately. Two circles can be tangent externally or internally, as shown below.

Image

If the circles are EXTERNALLY tangent, the distance is r1 + r2, or 8. If the circles are INTERNALLY tangent, the distance is |r1 - r2|, or 2. So the real answer is E.

Beware these seemingly easy questions on the test! If the answer were really C, they wouldn't bother asking you.
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