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

 It is currently 20 May 2019, 17:59 ### 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
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. ### Request Expert Reply # If ab^3c^4 > 0, is a^3bc^5 > 0?

 new topic post reply Question banks Downloads My Bookmarks Reviews Important topics
Author Message
TAGS:

### Hide Tags

Math Expert V
Joined: 02 Sep 2009
Posts: 55188
If ab^3c^4 > 0, is a^3bc^5 > 0?  [#permalink]

### Show Tags

3
7 00:00

Difficulty:   45% (medium)

Question Stats: 63% (01:20) correct 37% (01:34) wrong based on 256 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  D
Status: GMATINSIGHT Tutor
Joined: 08 Jul 2010
Posts: 2931
Location: India
GMAT: INSIGHT
Schools: Darden '21
WE: Education (Education)
If ab^3c^4 > 0, is a^3bc^5 > 0?  [#permalink]

### Show Tags

2
2
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

Answer: option
_________________
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, 04:25.
Last edited by GMATinsight on 11 Sep 2018, 08:24, edited 5 times in total.
Manager  B
Joined: 26 Dec 2011
Posts: 115
Schools: HBS '18, IIMA
Re: If ab^3c^4 > 0, is a^3bc^5 > 0?  [#permalink]

### Show Tags

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

Please give me Kudos
_________________
Thanks,
Kudos Please
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

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 V
Joined: 02 Sep 2009
Posts: 55188
Re: If ab^3c^4 > 0, is a^3bc^5 > 0?  [#permalink]

### Show Tags

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.

The correct answer is B.
_________________
Manager  S
Joined: 24 Oct 2013
Posts: 132
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

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  G
Joined: 26 Oct 2016
Posts: 633
Location: United States
Concentration: Marketing, International Business
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

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.
The correct answer is B.
_________________
Thanks & Regards,
Anaira Mitch
VP  P
Joined: 31 Oct 2013
Posts: 1352
Concentration: Accounting, Finance
GPA: 3.68
WE: Analyst (Accounting)
If ab^3c^4>0 is a^3bc^5>0 ?  [#permalink]

### Show Tags

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

1.b>0
2.c>0
Manager  G
Joined: 05 Feb 2016
Posts: 161
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

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 V
Joined: 02 Sep 2009
Posts: 55188
Re: If ab^3c^4 > 0, is a^3bc^5 > 0?  [#permalink]

### Show Tags

selim wrote:
If $$ab^3c^4>0 is a^3bc^5>0?$$

1.b>0
2.c>0

___________________________
Merging topics.
_________________
Director  P
Joined: 02 Oct 2017
Posts: 729
Re: If ab^3c^4 > 0, is a^3bc^5 > 0?  [#permalink]

### Show Tags

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  B
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

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

### Show Tags

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)
Intern  B
Joined: 20 Nov 2018
Posts: 10
Re: If ab^3c^4 > 0, is a^3bc^5 > 0?  [#permalink]

### Show Tags

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

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

Kudos for a correct solution.

$$ab^3c^4 > 0$$
gives,
$$ab^3 > 0$$ i.e., we have$$ab>0$$

i. a>0 b>0
ii. a<0 b<0

to find if
$$a^3bc^5 > 0$$
we already know that $$ab > 0$$
which implies $$a^3b > 0$$
so if c>0 the $$a^3bc^5 > 0$$ is true
else false

(1) given b>0 ---> insufficient
(2) given c>0 ----> sufficient

option is B
----------------------------------------
Please leave a kudos:) Re: If ab^3c^4 > 0, is a^3bc^5 > 0?   [#permalink] 21 Feb 2019, 03:48
Display posts from previous: Sort by

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

 new topic post reply Question banks Downloads My Bookmarks Reviews Important topics 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®.

#### MBA Resources  