GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 18 Jul 2018, 09:05

# STARTS SOON:

How to get into Ross | LIVE admitted student CHAT - 9 AM PST

### GMAT Club Daily Prep

#### 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

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

# Is a/b < 0?

Author Message
TAGS:

### Hide Tags

Senior Manager
Joined: 29 Jan 2011
Posts: 314

### Show Tags

Updated on: 20 Jun 2011, 22:30
3
00:00

Difficulty:

25% (medium)

Question Stats:

70% (00:37) correct 30% (01:32) wrong based on 404 sessions

### HideShow timer Statistics

Is a/b < 0?

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

(2) ab^4 < 0

Originally posted by siddhans on 19 Jun 2011, 16:32.
Last edited by siddhans on 20 Jun 2011, 22:30, edited 1 time in total.
Retired Moderator
Joined: 16 Nov 2010
Posts: 1467
Location: United States (IN)
Concentration: Strategy, Technology

### Show Tags

19 Jun 2011, 18:20
2

(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.

_________________

Formula of Life -> Achievement/Potential = k * Happiness (where k is a constant)

GMAT Club Premium Membership - big benefits and savings

Manager
Status: Pushing Hard
Affiliations: GNGO2, SSCRB
Joined: 30 Sep 2012
Posts: 81
Location: India
Concentration: Finance, Entrepreneurship
GPA: 3.33
WE: Analyst (Health Care)

### Show Tags

10 May 2013, 21:21
1

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 !!
_________________

If you don’t make mistakes, you’re not working hard. And Now that’s a Huge mistake.

Intern
Joined: 28 May 2013
Posts: 13
Re: Is a/b < 0? (1)a^2/b^3 > 0 (2) ab^4 < 0 [#permalink]

### Show Tags

08 Oct 2013, 08:35
Hi Bunuel/All ,

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

Regards
Akshay
GMAT Club Legend
Joined: 16 Oct 2010
Posts: 8127
Location: Pune, India
Re: Is a/b < 0? (1)a^2/b^3 > 0 (2) ab^4 < 0 [#permalink]

### Show Tags

08 Oct 2013, 23:51
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.
_________________

Karishma
Private Tutor for GMAT
Contact: bansal.karishma@gmail.com

Intern
Joined: 28 May 2013
Posts: 13
Re: Is a/b < 0? [#permalink]

### Show Tags

09 Oct 2013, 01:27
Thanks Karishma . I think sometimes it is better not to think too much and skip some possible scenarios .
Manager
Joined: 24 Apr 2013
Posts: 65
Location: United States
Re: Is a/b < 0? [#permalink]

### Show Tags

17 Oct 2013, 02:26
Clumsy mistake.
I read st 2 as (ab)^4 <0
_________________

Struggling: make or break attempt

Current Student
Status: DONE!
Joined: 05 Sep 2016
Posts: 398
Re: Is a/b < 0? [#permalink]

### Show Tags

23 Sep 2016, 10:26
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
Senior Manager
Joined: 05 Jan 2017
Posts: 426
Location: India
Re: Is a/b < 0? [#permalink]

### Show Tags

23 Feb 2017, 06:00
Prompt analysis
A and b are real numbers.
Superset
The answer will be either YES or NO.

Translation
In order to find the answer, we need:
1# exact value of a and b.
2# any equation to find the a and b
3# any equation to find the exact or the range for a/b

Statement analysis
St 1: a^2/b^3 >0. a^2 is always greater than zero. If the complete expression is positive, that means that b^3 is positive hence b is positive. But nothing can be said about a. INSUFFICIENT

St 2: ab^4<0. b^4 is always positive.nothing can be said about b though. To make the expression negative, a has to be negative.

St 1 & St 2: from st 1, we can say that b>0. From st 2, we can say that a<0. Therefore a/b <0.
Option C.
Manager
Joined: 29 Jan 2017
Posts: 51
Re: Is a/b < 0? [#permalink]

### Show Tags

10 Aug 2017, 22:00
St1.
A can be + or -
B is +

St2.
A is -
B can be + or -

Together, A must be - and B must be +

C

siddhans wrote:
Is a/b < 0?

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

(2) ab^4 < 0
Re: Is a/b < 0?   [#permalink] 10 Aug 2017, 22:00
Display posts from previous: Sort by

# Events & Promotions

 Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.