BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

700 - 800 Inequality

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Source: — Data Sufficiency |
Senior | Next Rank: 100 Posts
Posts: 43
Joined: Tue Oct 13, 2009 3:31 pm

by Talkativetree » Tue Oct 20, 2009 8:27 pm
pretty sure C.

(1) tells us B is positive (odd exponent), but A could still be + or -
(2) tells us A is negative(exponent is odd), but B could still be + or -

together we know that a +/-<0
Top
Legendary Member
Posts: 869
Joined: Wed Aug 26, 2009 3:49 pm
Location: California
Thanked: 13 times
Followed by:3 members

by heshamelaziry » Tue Oct 20, 2009 9:16 pm
Talkativetree wrote:pretty sure C.

(1) tells us B is positive (odd exponent), but A could still be + or -
(2) tells us A is negative(exponent is odd), but B could still be + or -

together we know that a +/-<0
The way I understand this is:

Statement 1: a^2 is always +ve means that b^3 has to be +ve for the statement to be true

Statement 2: b^4 is always +ve means that a has to be -ve for the statement to be true.

I still can't deduce that one of the variables is +ve and the other is -ve ?

From your answer how can we say that b is +ve from b^3, if for example b= -1 and (-1)^3 is -1 ?

Thanks for patience
Top
Junior | Next Rank: 30 Posts
Posts: 16
Joined: Wed Jul 15, 2009 12:10 pm

by tgf » Sat Oct 24, 2009 4:28 am
Because (taken together) from 2) you know that a<0 and for 1) to be positive b can't be negative (since a^2 is positive). So b>0.

Edit: Sorry the <, > signs should be replaced by +/- (sorry)
Top
Senior | Next Rank: 100 Posts
Posts: 43
Joined: Tue Oct 13, 2009 3:31 pm

by Talkativetree » Sat Oct 24, 2009 8:30 pm
we can deduce that B will always be + and A will always be - because the inequalities we are given in the two statements must be true. Also, what each statement gives us will never contradict the other statement, so we can make both assumptions
Top
Legendary Member
Posts: 1161
Joined: Mon May 12, 2008 2:52 am
Location: Sydney
Thanked: 23 times
Followed by:1 members

by mehravikas » Tue Oct 27, 2009 7:44 pm
IMO - C

The answer has been already explained above, and my solution is exactly the same.

OA please?
Top
Post new topic Post Reply
• Page 1 of 1