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

 It is currently 18 Dec 2018, 13:40

### 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

## Events & Promotions

###### Events & Promotions in December
PrevNext
SuMoTuWeThFrSa
2526272829301
2345678
9101112131415
16171819202122
23242526272829
303112345
Open Detailed Calendar
• ### Happy Christmas 20% Sale! Math Revolution All-In-One Products!

December 20, 2018

December 20, 2018

10:00 PM PST

11:00 PM PST

This is the most inexpensive and attractive price in the market. Get the course now!
• ### Key Strategies to Master GMAT SC

December 22, 2018

December 22, 2018

07:00 AM PST

09:00 AM PST

Attend this webinar to learn how to leverage Meaning and Logic to solve the most challenging Sentence Correction Questions.

# If ab^3c^4 > 0, is a^3bc^5 > 0?

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 51280
If ab^3c^4 > 0, is a^3bc^5 > 0?  [#permalink]

### Show Tags

12 Jun 2015, 02:38
3
4
00:00

Difficulty:

45% (medium)

Question Stats:

64% (00:58) correct 36% (01:08) wrong based on 314 sessions

### HideShow timer Statistics

If $$ab^3c^4 > 0$$, is $$a^3bc^5 > 0$$?

(1) b > 0
(2) c > 0

Kudos for a correct solution.

_________________
CEO
Status: GMATINSIGHT Tutor
Joined: 08 Jul 2010
Posts: 2711
Location: India
GMAT: INSIGHT
WE: Education (Education)
If ab^3c^4 > 0, is a^3bc^5 > 0?  [#permalink]

### Show Tags

Updated on: 11 Sep 2018, 07:24
1
1
Bunuel wrote:
If $$ab^3c^4 > 0$$, is $$a^3bc^5 > 0$$?

(1) b > 0
(2) c > 0

Kudos for a correct solution.

Given: $$ab^3c^4 > 0$$

i.e. a*b must be Positive [Odd powers don't change the sign of variable]
i.e. a and b have same sign

Question : is $$a^3bc^5 > 0$$

But $$a^3b$$ will always be positive as a and b have same sign

i.e. We only need to find the sign of c to answer the question

Statement 1: b > 0

Sign of c is unknown

Hence, NOT SUFFICIENT

Statement 2: c > 0

i.e. c is positive therefore $$a^3bc^5 > 0$$ is True

Hence, SUFFICIENT

_________________

Prosper!!!
GMATinsight
Bhoopendra Singh and Dr.Sushma Jha
e-mail: info@GMATinsight.com I Call us : +91-9999687183 / 9891333772
Online One-on-One Skype based classes and Classroom Coaching in South and West Delhi
http://www.GMATinsight.com/testimonials.html

ACCESS FREE GMAT TESTS HERE:22 ONLINE FREE (FULL LENGTH) GMAT CAT (PRACTICE TESTS) LINK COLLECTION

Originally posted by GMATinsight on 12 Jun 2015, 03:25.
Last edited by GMATinsight on 11 Sep 2018, 07:24, edited 5 times in total.
Manager
Joined: 26 Dec 2011
Posts: 114
Schools: HBS '18, IIMA
Re: If ab^3c^4 > 0, is a^3bc^5 > 0?  [#permalink]

### Show Tags

12 Jun 2015, 05:09
If ab^3c^4>0, is a^3bc^5>0?

(1) b > 0
(2) c > 0

Explanation -

Stmt 1 - If b is +ve, a is +ve and we do not know about c +ve or -ve. Not Sufficient

Stmt 2 - If c is +ve, both a and b must be +ve or -ve to meet the condition. Sufficient

Ans B
Thanks

_________________

Thanks,

Intern
Joined: 26 Aug 2014
Posts: 46
GMAT 1: 650 Q49 V30
GMAT 2: 650 Q49 V31
WE: Programming (Computer Software)
Re: If ab^3c^4 > 0, is a^3bc^5 > 0?  [#permalink]

### Show Tags

13 Jun 2015, 01:50
1
(i) ab^3c^4>0
(ii) a^3bc^5>0?

Here, powers of a and b are odd in both inequalities so, their sign won't change to negative.
(Notice c^4 will always be positive so multiplication of odd powers of a with odd powers of b will also be always positive to satisfy (i)).

However, the power of c changes in both inequalities from even in (i) to odd in (ii).
Hence, if c is positive (ii) will be positive, and if c is negative (ii) will be negative.

(1) b > 0
This gives us no information on the sign of c, and consequently, we cannot determine if (ii) is positive or negative. Not Sufficient

(2) c > 0
This tells us c is positive. Hence (ii) is positive. Sufficient

Press Kudos if you like it!
Math Expert
Joined: 02 Sep 2009
Posts: 51280
Re: If ab^3c^4 > 0, is a^3bc^5 > 0?  [#permalink]

### Show Tags

15 Jun 2015, 04:57
Bunuel wrote:
If $$ab^3c^4 > 0$$, is $$a^3bc^5 > 0$$?

(1) b > 0
(2) c > 0

Kudos for a correct solution.

MANHATTAN GMAT OFFICIAL SOLUTION:

Odd exponents do not “hide the sign” of the base. In other words, a and a^3 have the same sign, as do b and b^3, regardless of the signs of a and b. In comparing ab^3c^4 > 0 (the constraint) to a^3bc^5 (the question), the only unknown real difference is between c^4 and c^5. We know that c^4 must be positive (even exponent), so if we want c^5 to be positive, then c needs to be positive also. Our rephrased question is thus “Is c > 0?”

(1) INSUFFICIENT: No information about the sign of c.

(2) SUFFICIENT: Answers the rephrased question directly.

_________________
Manager
Joined: 24 Oct 2013
Posts: 135
Location: India
Concentration: General Management, Strategy
WE: Information Technology (Computer Software)
Re: If ab^3c^4 > 0, is a^3bc^5 > 0?  [#permalink]

### Show Tags

27 Sep 2016, 05:24
a and b are odd powers in both the expressions. only unknown sign is of c

Statement 2 states C >0 => final value is positive.

HEnce B
Director
Joined: 26 Oct 2016
Posts: 640
Location: United States
Schools: HBS '19
GMAT 1: 770 Q51 V44
GPA: 4
WE: Education (Education)
Re: If ab^3c^4 > 0, is a^3bc^5 > 0?  [#permalink]

### Show Tags

03 Mar 2017, 12:16
Odd exponents do not “hide the sign” of the base. In other words, a and a^3 have the same sign, as do b and b^3, regardless of the signs of a and b. In comparing ab^3c^4 > 0 (the constraint) to a^3bc^5 (the question), the only unknown real difference is between c^4 and c^5. We know that c^4 must be positive (even exponent), so if we want c^5 to be positive, then c needs to be positive also. Our rephrased question is thus “Is c > 0?”
(1) INSUFFICIENT: No information about the sign of c.
(2) SUFFICIENT: Answers the rephrased question directly.
_________________

Thanks & Regards,
Anaira Mitch

Director
Joined: 31 Oct 2013
Posts: 899
Concentration: Accounting, Finance
GPA: 3.68
WE: Analyst (Accounting)
If ab^3c^4>0 is a^3bc^5>0 ?  [#permalink]

### Show Tags

22 Apr 2018, 06:03
If $$ab^3c^4>0 is a^3bc^5>0?$$

1.b>0
2.c>0
Manager
Joined: 05 Feb 2016
Posts: 144
Location: India
Concentration: General Management, Marketing
WE: Information Technology (Computer Software)
Re: If ab^3c^4>0 is a^3bc^5>0 ?  [#permalink]

### Show Tags

22 Apr 2018, 06:17
selim wrote:
If $$ab^3c^4>0 is a^3bc^5>0?$$

1.b>0
2.c>0

from given statement either a>0,b>0 or a<0,b<0

From 1: we cant say anything.

From 2: since a and b have same sign Then a*b>0 . and c>0

Therefore $$a^3bc^5>0$$

Sufficient B.
Math Expert
Joined: 02 Sep 2009
Posts: 51280
Re: If ab^3c^4 > 0, is a^3bc^5 > 0?  [#permalink]

### Show Tags

22 Apr 2018, 20:49
selim wrote:
If $$ab^3c^4>0 is a^3bc^5>0?$$

1.b>0
2.c>0

___________________________
Merging topics.
_________________
Director
Joined: 02 Oct 2017
Posts: 730
Re: If ab^3c^4 > 0, is a^3bc^5 > 0?  [#permalink]

### Show Tags

08 May 2018, 08:52
ab^3c^4>0
Simply means a and b have same sign

So for a^3bc^5>0

Since a and b have same sign so only thing we need to know whether c>0 or not

Choice B states this

Posted from my mobile device
_________________

Give kudos if you like the post

Intern
Joined: 14 Mar 2015
Posts: 5
Location: India
Schools: ISB '19 (I)
GMAT 1: 710 Q50 V35
GPA: 3.57
Re: If ab^3c^4 > 0, is a^3bc^5 > 0?  [#permalink]

### Show Tags

11 Sep 2018, 09:17
Bunuel wrote:
If $$ab^3c^4 > 0$$, is $$a^3bc^5 > 0$$?

(1) b > 0
(2) c > 0

Kudos for a correct solution.

Hi,

Given ab^3c^4 > 0. We already know that any integer multiplied to even power is always positive.

Hence from above we already now that b^2 and c^4 are always positive. Hence this inequation input can be simplified to ab>0. This is the given input.

Now the question " is a^3bc^5 > 0"?

Again applying above discussed funda, the question can be simplified to is abc>0?

So the question is if ab>0, is abc >o?

From options, it is clear that "option 1 : b >0 " is not sufficient whereas "option 2 : c>0" alone is sufficient to answer.

Hence option "B"
Intern
Joined: 19 Sep 2014
Posts: 2
WE: Engineering (Manufacturing)
Re: If ab^3c^4 > 0, is a^3bc^5 > 0?  [#permalink]

### Show Tags

27 Sep 2018, 05:15
If ab^3c^4 > 0, is a^3bc^5 > 0?

Now coming to first equation: as c^4 term is present, being exponent an even power it has no effect on overall equation.
Hence coming on ab, as ab>0 then definitely a & b are of same sign either both + or both -.

Hence deciding factor is c for the next equation as it has odd exponent, only if its is> 0 then only the whole equation is > 0.

So Statement 2 is true.

Ans. (B)
Re: If ab^3c^4 > 0, is a^3bc^5 > 0? &nbs [#permalink] 27 Sep 2018, 05:15
Display posts from previous: Sort by