DS

[ketkoag]

Is the measure of one of the interior angles of quadrilateral ABCD equal to 60 degrees?
(1) Two of the interior angles of ABCD are right angles.
(2) The degree measure of angle ABC is twice the degree measure of angle BCD.
A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is
sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOT sufficient.

Now the OA is c but my answer is E because,I've considered both the statements and let say a quad with angles 90, 90, 45, 135. now in this case angle abc is 90, angle bcd is 45, angle cda is 135, angle dab is 90. therefore one of the angle is not 60. this is the first case.....
now the second case is the quad with angles angle abc 120, angle bcd 60, angle cda 90, angle dab 90. therefore one angle is 60.
So if we take both the statements, they are not sufficient to answer this question.

Please explain whether there is any alternate explaination of if this one is not correct.

[Ian Stewart]

I'm not sure where you're getting your OAs from, but that question is in GMATPrep, and the OA is certainly E, not C, for exactly the reason you mention - the angles could be 90,90,120,60, or they could be 90,90,45,135.

[ketkoag]

thanks for the reply Ian.....
I got this question from the gmat practice set, and the answer given is c.
anyways, thanks again