DS problem from Geometry

Expert replies

s.pharmaco: Junior | Next Rank: 30 Posts; Posts: 10; Joined: Sun Jul 08, 2012 12:35 am

by s.pharmaco » Thu Aug 02, 2012 9:00 am

Well I have a problem where I am not able to understand the solution

The problem is: In the attached figure

In PQR , if PQ = QR, what is Z?
(1) x = 65 (2) y = 57

The answer is that both are rquired to answer the question, however i think only A is required because since PQ=QR z would be equal to angle QRP which is equal to y because of opposite angles. Since x is an external angle i.e. equal to z + angle QRP it will be equal to 2z. I i know value of x then I can calculate z. Can anyone please help why its answer is C and not A

Attachments

Problem figure.doc: (27 KiB) Downloaded 127 times

Like this post

Source: Beat The GMAT — Data Sufficiency | Thu Aug 02, 2012 9:00 am

avinashrao9: Newbie | Next Rank: 10 Posts; Posts: 8; Joined: Wed May 02, 2012 12:08 am

by avinashrao9 » Thu Aug 02, 2012 10:20 am

If QRP = y = z because of alternate angles, even PQR = x because of alternate angles.
Since it is an isoceles triangle,
According to (1), it is 2z + x = 180 => z = 57.5
According to (2), z = y = 57

Why not answer (D). Individual choices are SUFFICIENT.

Like this post

shatyasree: Newbie | Next Rank: 10 Posts; Posts: 3; Joined: Thu Aug 16, 2012 2:14 am

by shatyasree » Thu Aug 16, 2012 2:17 am

D is correct since statement alone is sufficient

Like this post

Patrick_GMATFix: GMAT Instructor; Posts: 1052; Joined: Fri May 21, 2010 1:30 amFollowed by: 98 members; Thanked: 335 times

by Patrick_GMATFix » Thu Aug 16, 2012 8:31 am

Notice that since we're dealing with an isosceles triangle, the two angles at the bottom are the same. As a result, we only need to know 1 of the angles in the triangle to discover all three.

Rephrase: What is any one angle in the triangle?

Each statement gives you an angle in the triangle since vertical angles (angles that face each other across two intersecting lines) are always equal.

D is correct.

Check out my site: GMATFix.com

To prep my students I use this tool >> (screenshots, video)

Ask me about tutoring.

Like this post

Post new topic Post Reply

• Page 1 of 1

GMAT Course Reviews

563 reviews

1168 reviews

431 reviews

359 reviews

147 reviews

5/5

5 Star (563 Reviews)

"Target Test Prep is the closest to the official version of the GMAT exam, about 99% accuracy in terms of the quality and quantity of information. The course has excellently created singular sets of focused lessons and tests for every possible topic that one could come across in the official GMAT exam."

"The TTP course maximizes the efficiency of the time you spend studying. It will take time and effort but I could almost guarantee that if you complete the course exactly as it is laid out you will get an amazing score. They also have a very responsive team willing to help with any questions you might have."

"TTP has two things that I think no other test prep company offers: A teaching approach that reinforces understanding and an attitude that will give you the mental preparedness needed to succeed on the test. TTP gives you a deep understanding of the concept you need to know while teaching you how to think."

Write a Review