Is a/b < 0? : GMAT Data Sufficiency (DS)
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Is a/b < 0?

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Is a/b < 0? [#permalink]

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Is a/b < 0?

(1) a^2/b^3 > 0

(2) ab^4 < 0
[Reveal] Spoiler: OA

Last edited by siddhans on 20 Jun 2011, 21:30, edited 1 time in total.
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Re: MGMAT DS [#permalink]

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New post 19 Jun 2011, 17:20
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The answer is C.

(1) says that b > 0, since a^2 is always positive, so we don't know the sign of a. Insufficient.

(2) says a is negative as b^4 is always positive, so we don't know the sign of b. Insufficient.

(1) + (2) Sufficient as we know signs of both a and b.

Answer - C.
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Positives and Negatives [#permalink]

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New post 10 May 2013, 12:09
Is [a]/[b] < 0?


(1) a[square_root]/[b3]> 0
(2) ab4 < 0
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Re: Positives and Negatives [#permalink]

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New post 10 May 2013, 20:21
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The question basically asks ....

IS \(lal\) < 0 ??

or a < 0 & a > 0 ......Does the value of a >0 & a <0 .....

Statement : 1 says ...... \(\sqrt{{a}} / l{b^3}l\) > 0

or \(\sqrt{{a}}\)> 0

or a > 0 ... Clearly Insufficient as it doesn't tell us if a< 0 also......Therefore, Insufficient.

Statement :: 2 ... Similar to statement it just tells us one part ... i.e;

as Given ... \(ab^4\) < 0 ... or a <0 .... Clearly, Insufficient.

1+2 ...... gives us that a<0 & a > 0 ..... Therefore, Sufficient.......

Hence, C ................. Hope it Helps !!
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Re: Positives and Negatives [#permalink]

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New post 11 May 2013, 02:55
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Re: Is a/b < 0? (1)a^2/b^3 > 0 (2) ab^4 < 0 [#permalink]

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New post 08 Oct 2013, 07:35
Hi Bunuel/All ,

Why are we not considering a & b to be fractions?

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Akshay
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Re: Is a/b < 0? (1)a^2/b^3 > 0 (2) ab^4 < 0 [#permalink]

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New post 08 Oct 2013, 22:51
AkshayChittoria wrote:
Hi Bunuel/All ,

Why are we not considering a & b to be fractions?

Regards
Akshay


Responding to a pm:

a and b could be fractions. We are not assuming that they must be integers. We are only talking about their sign.

(1)a^2/b^3 > 0

It doesn't matter whether a and b are fractions or integers, a^2 will be positive. So b must be positive since positive/b^3 is positive. But we don't know whether a is positive or negative. Can't say about the sign of a/b

(2) ab^4 < 0

b^4 must be positive. So a must be negative because a/positive is negative. Can't say about the sign of a/b

Both together, b is positive and a is negative so a/b must be negative. Sufficient.
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Re: Is a/b < 0? [#permalink]

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New post 09 Oct 2013, 00:27
Thanks Karishma :) . I think sometimes it is better not to think too much and skip some possible scenarios :P :P .
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Re: Is a/b < 0? [#permalink]

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New post 17 Oct 2013, 01:26
Clumsy mistake.
I read st 2 as (ab)^4 <0
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Re: Is a/b < 0? [#permalink]

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New post 23 Sep 2016, 09:26
C is correct. Here's why:

(1) a^2/b^3 > 0

From this we know that b < 0, but we don't know whether a<0 or a>0, thus INSUFFICIENT

(2) ab^4 < 0

From this we know a < 0, but we don't know whether b>0 or b<0, thus INSUFFICIENT

(1) + (2) - We know a<0 and b>0, therefore we know a/b<0 SUFFICIENT
Re: Is a/b < 0?   [#permalink] 23 Sep 2016, 09:26
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