Gmat prep

Expert replies

Previous Topic Next Topic

awilhelm: Master | Next Rank: 500 Posts; Posts: 117; Joined: Fri Oct 17, 2008 7:41 am

by awilhelm » Mon Jan 26, 2009 10:00 pm

Is m + z > 0?

1) m - 3z > 0
2) 4z - m > 0

Like this post

Source: Beat The GMAT — Data Sufficiency | Mon Jan 26, 2009 10:00 pm

DanaJ: Site Admin; Posts: 2567; Joined: Thu Jan 01, 2009 10:05 amFollowed by: 550 members; Thanked: 712 times; GMAT Score:770

by DanaJ » Tue Jan 27, 2009 12:05 am

1. Well, I believe we're better off trying a few numeric examples for this one. Say m = 5 and z = 1. This means that m - 3z = 2 > 0 and m + z = 6 > 0.
Now let's take another example: Say m = 5 and z = -6.
m - 3z = 5 + 18 = 23 > 0. But m + z = 5 - 6 = -1 <0. So 1 is not sufficient.

2. is not sufficient using the same line of thought as above.

Now, let's take the two statements together. Adding the two is equivalent to z > 0. Since z is positive, this means that, using statement 1, m can only be positive as well. Adding the two positive numbers will always be a positive number, so both statements taken together are sufficient.

Like this post

4meonly: Legendary Member; Posts: 891; Joined: Sat Aug 16, 2008 4:21 amFollowed by: 1 member; Thanked: 27 times; GMAT Score:660(

by 4meonly » Tue Jan 27, 2009 1:07 am

Agree with C
Just draw the number line.

Stem 1 can guve you positive and negative meaning for m and z and their sum can be as positive as negative.

Stem 2: the same approach as with stem1.

Combined:
3z < m < 4z
Ths can be only if both are positive. So, sum is also positive.

4 Sale: GMAT Club Access

Like this post

sanju09: GMAT Instructor; Posts: 3650; Joined: Wed Jan 21, 2009 4:27 amFollowed by: 80 members; Location: India; Thanked: 267 times; GMAT Score:760

by sanju09 » Tue Jan 27, 2009 6:27 am

4meonly wrote:Agree with C
Just draw the number line.

Stem 1 can guve you positive and negative meaning for m and z and their sum can be as positive as negative.

Stem 2: the same approach as with stem1.

Combined:
3z < m < 4z
Ths can be only if both are positive. So, sum is also positive.

Both explanations are master class and less time consuming. Remember, it's always worthwhile to use permissible number(s), in case you cannot visualize a rule, this is why I found the first work as awesome. The second work is accomplished by keeping rules in mind, which is always admirable on GMAT.

The mind is everything. What you think you become. -Lord Buddha

Sanjeev K Saxena
Quantitative Instructor
The Princeton Review - Manya Abroad
Lucknow-226001

www.manyagroup.com

Like this post

Post new topic Post Reply

• Page 1 of 1

GMAT Course Reviews

560 reviews

1168 reviews

431 reviews

359 reviews

147 reviews

5/5

5 Star (560 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