Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized for You

we will pick new questions that match your level based on your Timer History

Track Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

Re: Another DS question....probably not hard...I just don't know [#permalink]
07 Jul 2008, 12:01

1

This post received KUDOS

jallenmorris wrote:

Q. Is a^2*b > 0? 1) |a|=b 2) ab<0

1. Insufficient: because a can be either 0 or any other number (+ve or -ve) 2. Insufficient: because ab < 0 gives us that one of them is -ve but we don't know which.

Combined: Sufficient: because from 1 & 2, b can't be -ve so a should be -ve and so a^2*b is > 0 It is C.

Re: Another DS question....probably not hard...I just don't know [#permalink]
07 Jul 2008, 12:23

maratikus wrote:

jallenmorris wrote:

Q. Is a^2*b > 0? 1) |a|=b 2) ab<0

1: insufficient a = b = 1 or a = b = 0 (b >=0) 2: insufficient a = 1, b = -1 or a = -1, b = 1 (a, b are not equal to 0)

1&2: since b >= 0 and b is not equal to zero -> b > 0, a is not equal to 0 -> a^2*b > 0 -> C

With respect to 1 & 2...You're saying neither A nor B can = 0 because anything * 0 = 0 and we're told in 2) that ab <0 (which is not zero). Then with 1, b = |a| and the absolute value of A cannot be nagative. So we know from the 2 statements that B is not 0, and it is not negative. That makes a be negative and not zero (not zero from #2).

Thanks. That helps me out a bunch. +1 for you. _________________

------------------------------------ J Allen Morris **I'm pretty sure I'm right, but then again, I'm just a guy with his head up his a$$.

Re: Another DS question....probably not hard...I just don't know [#permalink]
07 Jul 2008, 13:51

Q. Is a^2*b > 0? 1) |a|=b 2) ab<0

From 1)

b must be possitive. a's value doesn't matter because a^2 is anyways going to be positive. So far 1) is suff but ... we dont know if a is a non zero or not. hence 1) is not suff.

From 2)

either a or b has to be negative. And neither a or b is zero. if a is -ve and b is +ve then a^2*b > 0 if a is +ve and b is -ve then a^2*b < 0

I couldn’t help myself but stay impressed. young leader who can now basically speak Chinese and handle things alone (I’m Korean Canadian by the way, so...