Triangle -Find Angle

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aim800: Newbie | Next Rank: 10 Posts; Posts: 1; Joined: Sat Apr 26, 2008 2:30 am

by aim800 » Wed Sep 10, 2008 7:35 am

how can arrive at the answer when it's not given that 2 lines are perpendicular

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Source: Beat The GMAT — Data Sufficiency | Wed Sep 10, 2008 7:35 am

GMATDavid: GMAT Instructor; Posts: 26; Joined: Sun Jul 06, 2008 8:53 am; Location: New York City; Thanked: 1 times

by GMATDavid » Wed Sep 10, 2008 7:48 am

Hi,

Focus on the interior angles of the triangle. Let's call them A (near x), B (near Y) and C (near Z). Notice that Angles x and A total 180 degrees because they form a line. Same with B and y. And same with C and z. Also, there are 180 degrees in the triangle.

Knowing that x=y tells us that A=B. But there are many possible degrees for A and B if we don't know what angle C is. So, we are down to answer choices BCE.

Knowing that x=z tells us that A=C. Same problem, however; we would need info about angle B. So, we are down to answer choices CE.

If x=y and x=z, then A=B and A=C, which means A, B, C are equal. Because there are 180 degrees in the triangle, each of A, B and C measures 60 degrees. Thus, we have sufficient information to find x (which is 120 degrees).

So, answer (C).

David Stoll
The Princeton Review

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pseudononymous: Senior | Next Rank: 100 Posts; Posts: 33; Joined: Fri Sep 05, 2008 6:40 am; Thanked: 1 times

by pseudononymous » Wed Sep 10, 2008 8:54 am

It never says that the figure is a triangle, so you won't be able to figure it out.

E

Edit: Now I'm doubting myself. Since the angles are given, perhaps you can assume that the lines touch.

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