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Source: — Data Sufficiency |
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by liferocks » Sun May 23, 2010 10:17 pm
From 1
(a+b)^2 - (a-b)^2 <0
or 4ab<0
or ab<0...sufficient

From 2
(a/b)=1..hence a and b has same sign..ab is positive...sufficient

Ans option D
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by vivek1110 » Sun May 23, 2010 10:58 pm
Nope that doesn't sound right.
From 1
(a+b)^2 - (a-b)^2 <0
or 4ab<0
or ab<0...sufficient
if a is positive, and b is negative ab<0
if both a and b are positive ab>0

You get two answers so insufficient.

Answer is D
Last edited by vivek1110 on Sun May 23, 2010 11:29 pm, edited 1 time in total.
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by thephoenix » Sun May 23, 2010 11:12 pm
vivek1110 wrote: if a is positive, and b is negative ab<0
if both a and b are positive ab>0

You get two answers so insufficient.

Answer is NOT C.
we have gto find whether a*b>0 or not
from 1 we get ab<0 hence a*b is not +ve........therefore suff
from 1 bth a and b can not be of same sign
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by vivek1110 » Sun May 23, 2010 11:32 pm
we have gto find whether a*b>0 or not
from 1 we get ab<0 hence a*b is not +ve........therefore suff
from 1 bth a and b can not be of same sign
Whoops, yeah that's right.
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by neha.patni » Sun May 23, 2010 11:32 pm
vivek1110 wrote:Is (a*b) Positive?

1. (a+b)^2 < (a-b)^2
2. (a/b)=1


Anybody?
IMO A
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by vivek1110 » Sun May 23, 2010 11:34 pm
neha.patni wrote:
vivek1110 wrote:Is (a*b) Positive?

1. (a+b)^2 < (a-b)^2
2. (a/b)=1


Anybody?
IMO A
OA: D
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by Patrick_GMATFix » Sun May 23, 2010 11:48 pm
This question would never appear on the GMAT because the 2 statements contradict each other. (2) tells us that a=b. If that is true, then statement (1) must be false. Because on the GMAT both statements must be true, this is not a GMAT caliber question.

In addition, the statements would each be sufficient, but give a different answer; another indication that this is not a good practice question.
(1) means a and b have opposite signs
(2) means a and b have same sign.

I would advise that you stop using whatever resource gave you this practice question. The best practice questions are official questions: the OGs and GMATPrep, along with tools that allow you to organize those questions by topic/difficulty and that give you good strategies/take-aways for each question.

Good Luck,
-Patrick
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