Quadrilateral with 2 sides that are 90 degrees?

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havok: Senior | Next Rank: 100 Posts; Posts: 94; Joined: Tue Jun 30, 2009 4:51 pm; Thanked: 24 times; Followed by:7 members; GMAT Score:750

Quadrilateral with 2 sides that are 90 degrees?

by havok » Sat Apr 09, 2011 11:11 am

Is the measure of on of the interior angles of quadrilateral ABCD equal to 60 degrees?

(1) two of the interior angles in ABCD are right angles
(2) the degree measure of ABC is twice the degree of angle BCD

Answer is E

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Source: Beat The GMAT — Data Sufficiency | Sat Apr 09, 2011 11:11 am

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Ian Stewart: GMAT Instructor; Posts: 2623; Joined: Mon Jun 02, 2008 3:17 am; Location: Montreal; Thanked: 1090 times; Followed by:355 members; GMAT Score:780

by Ian Stewart » Sat Apr 09, 2011 11:50 am

havok wrote:Is the measure of on of the interior angles of quadrilateral ABCD equal to 60 degrees?

(1) two of the interior angles in ABCD are right angles
(2) the degree measure of ABC is twice the degree of angle BCD

Answer is E

I think many people assume, looking at both statements together, that the angles must be 90, 90, 60 and 120. There's a second possibility: angle ABC might be one of the right angles, in which case ABC is 90, BCD is 45, and the other two angles are 90 and 135. So the answer is E.

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