ABCD is a quadrilateral. Is the sum of angles ABC and CDA is

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ABCD is a quadrilateral. Is the sum of angles ABC and CDA is [#permalink]

24 Mar 2008, 09:13

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ABCD is a quadrilateral. Is the sum of angles ABC and CDA is equal to the sum of angles BCD and DAB?

(1) Circle O is inscribed in ABCD.

(2) Circle O is circumscribed about ABCD.

Please explain your answer. I thought this question was straight forward, but apparently I got tricked.
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Re: DS: Quadrilateral [#permalink]

24 Mar 2008, 10:12

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For a square the sum of angles ABC and CDA is equal to the sum of angles BCD and DAB under both conditions.

1. we can construct a rhombus (see a drawing) in which the sums will not be equal. insufficient
2. for any quadrilateral inscribed in a circle, the sums will always be equal (see the drawing). sufficient

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Re: DS: Quadrilateral [#permalink]

24 Mar 2008, 10:35

dude, you're just insane! hehe...the OA is B. Is there any quant problem that you just can't answer?? there has to be one...lol...thanks anyway...

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Re: DS: Quadrilateral [#permalink]

24 Mar 2008, 10:36

what is the difference between inscribed and circumscribed?
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Re: DS: Quadrilateral [#permalink]

24 Mar 2008, 11:48

bmwhype2 wrote:

what is the difference between inscribed and circumscribed?

http://en.wikipedia.org/wiki/Inscribe
http://en.wikipedia.org/wiki/Circumscribe

BTW. Thanks, I corrected my typo...
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Re: DS: Quadrilateral [#permalink] 24 Mar 2008, 11:48

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ABCD is a quadrilateral. Is the sum of angles ABC and CDA is

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ABCD is a quadrilateral. Is the sum of angles ABC and CDA is

ABCD is a quadrilateral. Is the sum of angles ABC and CDA is

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