• Board contributors include instructors with "800" GMAT scores.
  • 95% of posts have replies within 24 hours.
  • Join for discounts with 800score, VeritasPrep and ManhattanGMAT


FAQ  - Register  - Search - Login 

All times are UTC - 7 hours




Post new topic Reply to topic  [ 2 posts ] 
Author Message
 Post subject: GMAT Algebra
PostPosted: Thu Apr 25, 2013 12:08 pm 
Offline
User avatar

Joined: Tue Apr 13, 2010 8:48 am
Posts: 483
If r + s = 4, is s < 0?
(1) -4 > -r
(2) r > 2s + 2

A. Statement (1) BY ITSELF is sufficient to answer the question, but statement (2) by itself is not.
B. Statement (2) BY ITSELF is sufficient to answer the question, but statement (1) by itself is not.
C. Statements (1) and (2) TAKEN TOGETHER are sufficient to answer the question, even though NEITHER statement BY ITSELF is sufficient.
D. Either statement BY ITSELF is sufficient to answer the question.
E. Statements (1) and (2) TAKEN TOGETHER are NOT sufficient to answer the question, meaning that further information would be needed to answer the question.


(A) Statement (1) tells us that -4 > -r. When we multiply this inequality by -1, we get r > 4 (remember to switch the direction of the inequality when multiplying or dividing by a negative).

When r > 4, s must be negative, otherwise r + s would be greater than 4. So this statement alone is sufficient.

Statement (2) tells us that r > 2s + 2. We could pick numbers here, but the algebra is probably easier.

Since r = 4 – s (from the question stem) and r > 2s + 2 (from the statement), we can substitute to find the range for s:
r > 2s + 2
4 – s > 2s + 2
2 > 3s
2/3 > s.

Knowing that s is less than 2/3 does not tell us whether it is positive or negative, so Statement (2) is insufficient.

Since Statement (1) is sufficient and Statement (2) is insufficient, the correct answer is choice (A).
----------

I think you are wrong here: r > 2s + 2 being 2/3 > s is telling you that s cannot be < 0, because which also answers the question.there is no negative number that you add to 2/3 and get 4 (r + s = 4 and 2/3 + s = 4)


Top
 Profile  
 
 Post subject: Re: GMAT Algebra
PostPosted: Thu Apr 25, 2013 12:11 pm 
Offline
User avatar

Joined: Fri Apr 09, 2010 2:11 pm
Posts: 459
Quote:
2/3 > s is telling you that s cannot be < 0
We have the inequality for s:
2/3 > s
Image

It tells us that s can be less than 0, or it can be from 0 (inclusive) to 2/3 (not inclusive).

Here are the examples of r and s that fit:
s = -1 and r = 5
s = 0 and r = 4
s = 1/2 and r = 3 1/2
Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 2 posts ] 

All times are UTC - 7 hours


Who is online

Users browsing this forum: No registered users and 0 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group
Template made by DEVPPL -
phpBB SEO
 
GMAT(TM) and GMAT CAT (TM) are registered trademarks of the Graduate Management Admission Council(TM). The Graduate Management Admission Council(TM) does not endorse, nor is affiliated in any way with the owner or any content of this site.