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Concentric circles

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by shivani.magan » Tue Feb 21, 2012 11:15 am
A circle is drawn inside a larger circle. If B and C are points on the smaller circle, and A and D are points on the larger circle, are the two circles concentric?

(1) A, B, C and D all lie on the same line.

(2) AD is a diameter in the larger circle, and BC is a diameter in the smaller circle.


OA is E. I think the ans should be C because BC and Ad are diameters and if they lie on the same line then the centers lie on the same lines , hence the circles are concentric ? Can someone explain why I am wrong here ?
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by Jim@StratusPrep » Tue Feb 21, 2012 11:35 am
Concentric circles share a center and with this description, the smaller circle does not have to be exactly in the center of the larger circle.
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by rijul007 » Tue Feb 21, 2012 11:38 am
shivani.magan wrote:A circle is drawn inside a larger circle. If B and C are points on the smaller circle, and A and D are points on the larger circle, are the two circles concentric?

(1) A, B, C and D all lie on the same line.

(2) AD is a diameter in the larger circle, and BC is a diameter in the smaller circle.


OA is E. I think the ans should be C because BC and Ad are diameters and if they lie on the same line then the centers lie on the same lines , hence the circles are concentric ? Can someone explain why I am wrong here ?

STATEMENT 1
(1) A, B, C and D all lie on the same line.

Possiblilities
Image

Insuff


STATEMENT 2
(2) AD is a diameter in the larger circle, and BC is a diameter in the smaller circle.

Possibilities

Image

Insuff

Combining the two statements

Image

Insuff

Option E
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by amit28it » Thu Feb 23, 2012 10:56 pm
hi buddy ,
You have posted a good question regarding circular questions .I think it is one of the questions of GMAT.I am also searching these questions in mass to prepare for it .Otherewise simple questions regarding Circumference of a Circle Formula and it's use will be very much useful to practice for us .Thanks .
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by ollapodrida » Fri Feb 24, 2012 11:42 am
@rijul007: I think there is a problem with your solution. The question says that B and C are on the small circle; A and D are on the large circle. Your plots don't show the points on the circles?
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by rijul007 » Sat Feb 25, 2012 12:17 am
ollapodrida wrote:@rijul007: I think there is a problem with your solution. The question says that B and C are on the small circle; A and D are on the large circle. Your plots don't show the points on the circles?
there is nothing wrong with the solution..
I have ploted the points correctly in all the circles,
except for the circle in statement 2, i missed plotting points A, D on the larger circle( am just human :D )
but it doesnt really matter if you get the idea about what i did. :)
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