gmat prep 2

This topic has expert replies
Source: — Data Sufficiency |

User avatar
GMAT Instructor
Posts: 15539
Joined: Tue May 25, 2010 12:04 pm
Location: New York, NY
Thanked: 13060 times
Followed by:1906 members
GMAT Score:790

by GMATGuruNY » Fri Sep 02, 2011 7:20 am
jainrahul1985 wrote:If zy < xy < 0, is |x - z | + |x | = |z | ?

(1) z < x

(2) y > 0

OA D
This is a strange question.
The question stem itself gives sufficient information.
|x-z| = the positive distance between x and z.

From the question stem: zy < xy < 0.

If y<0:
Then x>0, z>0, and z>x, so that zy < xy < 0.
For example, if we plug y=-1, x=1 and z=2 into zy < xy < 0, we get:
-2 < -1 < 0.
Viewed on the number line:
Image
The drawing above shows that |x-z| + |x| = |z|.

If y>0:
Then x<0, z<0 and z<x, so that zy < xy < 0.
For example, if we plug y=1, x=-1 and z=-2 into zy < xy < 0, we get:
-2 < -1 < 0.
Viewed on the number line:
Image
The drawing above shows that |x-z| + |x| = |z|.

The information in the question stem itself proves that |x-z| + |x| = |z|.
The statements are irrelevant.
Thus, statement 1 is "sufficient", because -- no matter what information it offers -- |x-z| + |x| = |z|.
Thus, statement 2 is "sufficient", because -- no matter what information it offers -- |x-z| + |x| = |z|.

The correct answer is D.
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.

As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.

For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3