It is currently 27 Sep 2021, 01:51 |

Customized

for You

Track

Your Progress

Practice

Pays

- Sep
**28**### Sign Up for 1 Week GRE Free Trial

09:00 PM PDT

-10:00 PM PDT

Free 1-week access to over 20 lesson videos and 20 practice questions. No payment info required. - Oct
**06**### Free GMAT/GRE Webinars & Classes

06:00 PM PDT

-08:00 PM PDT

YouTube links to all completed GRE & GMAT-related webinars and classes, hosted by our Director of Online Tutoring, will be posted here in chronological order, from most to least recent. - Oct
**06**### Ignite Your GRE® Quant Score

08:00 PM PDT

-11:00 PM PDT

Target Test Prep GRE Quant is a unique, comprehensive online course that combines innovative software with time-tested study methods to prepare you for the rigors of the GRE. Try our course for 5 days for just $1(no automatic billing)

a^3b^4c^7>0
[#permalink]
18 Jul 2018, 17:00

Expert Reply

Question Stats:

\(a^3b^4c^7>0\)

Which of the following statements must be true?

Indicate all such statements.

A. \(ab\) is negative

B. \(abc\) is positive

C. \(ac\) is positive

_________________

Which of the following statements must be true?

Indicate all such statements.

A. \(ab\) is negative

B. \(abc\) is positive

C. \(ac\) is positive

_________________

GRE Prep Club OFFICIAL Android App

New to the GRE, and GRE CLUB Forum?

GRE: All you do need to know about the GRE Test | GRE Prep Club for the GRE Exam - The Complete FAQ

Search GRE Specific Questions | Download Vault

Posting Rules: QUANTITATIVE | VERBAL

FREE Resources: GRE Prep Club Official LinkTree Page | Free GRE Materials - Where to get it!! (2020)

Free GRE Prep Club Tests: Got 20 Kudos? You can get Free GRE Prep Club Tests

GRE Prep Club on : Facebook | Instagram

Questions' Banks and Collection:

ETS: ETS Free PowerPrep 1 & 2 All 320 Questions Explanation. | ETS All Official Guides

3rd Party Resource's: All Quant Questions Collection | All Verbal Questions Collection

Books: All GRE Best Books

Scores: The GRE average score at Top 25 Business Schools 2020 Ed. | How to study for GRE retake and score HIGHER - (2020)

How is the GRE Score Calculated -The Definitive Guide (2021)

Tests: GRE Prep Club Tests | FREE GRE Practice Tests [Collection] - New Edition (2021)

Vocab: GRE Prep Club Official Vocabulary Lists for the GRE (2021)

New to the GRE, and GRE CLUB Forum?

GRE: All you do need to know about the GRE Test | GRE Prep Club for the GRE Exam - The Complete FAQ

Search GRE Specific Questions | Download Vault

Posting Rules: QUANTITATIVE | VERBAL

FREE Resources: GRE Prep Club Official LinkTree Page | Free GRE Materials - Where to get it!! (2020)

Free GRE Prep Club Tests: Got 20 Kudos? You can get Free GRE Prep Club Tests

GRE Prep Club on : Facebook | Instagram

Questions' Banks and Collection:

ETS: ETS Free PowerPrep 1 & 2 All 320 Questions Explanation. | ETS All Official Guides

3rd Party Resource's: All Quant Questions Collection | All Verbal Questions Collection

Books: All GRE Best Books

Scores: The GRE average score at Top 25 Business Schools 2020 Ed. | How to study for GRE retake and score HIGHER - (2020)

How is the GRE Score Calculated -The Definitive Guide (2021)

Tests: GRE Prep Club Tests | FREE GRE Practice Tests [Collection] - New Edition (2021)

Vocab: GRE Prep Club Official Vocabulary Lists for the GRE (2021)

Re: a^3b^4c^7>0
[#permalink]
18 Jul 2018, 19:53

2

Carcass wrote:

\(a^3b^4c^7>0\)

Which of the following statements must be true?

Indicate all such statements.

A. \(ab\) is negative

B. \(abc\) is positive

C. \(ac\) is positive

Which of the following statements must be true?

Indicate all such statements.

A. \(ab\) is negative

B. \(abc\) is positive

C. \(ac\) is positive

the above statement will be true if any of the following statement are true,

1. a , b , c are all positive numbers

2. if a is +ve, b is -ve and c is +ve

3. if a is -ve, b is +ve and c is -ve

Therefore only option C is always true

_________________

If you found this post useful, please let me know by pressing the Kudos Button

Rules for Posting

Got 20 Kudos? You can get Free GRE Prep Club Tests

GRE Prep Club Members of the Month:TOP 10 members of the month with highest kudos receive access to 3 months GRE Prep Club tests

Rules for Posting

Got 20 Kudos? You can get Free GRE Prep Club Tests

GRE Prep Club Members of the Month:TOP 10 members of the month with highest kudos receive access to 3 months GRE Prep Club tests

Re: a^3b^4c^7>0
[#permalink]
29 Aug 2018, 07:38

4

Expert Reply

Carcass wrote:

\(a^3b^4c^7>0\)

Which of the following statements must be true?

Indicate all such statements.

A. \(ab\) is negative

B. \(abc\) is positive

C. \(ac\) is positive

Which of the following statements must be true?

Indicate all such statements.

A. \(ab\) is negative

B. \(abc\) is positive

C. \(ac\) is positive

Key Concept: (any number)^(EVEN INTEGER) ≥ 0

First, since \(a^3b^4c^7>0\), we know that a ≠ 0, b ≠ 0, and c ≠ 0

Next, since \(b^4\) must be POSITIVE, we can safely divide both sides of the inequality by \(b^4\) to get: \(a^3c^7>0\)

Also, since \(c^6\) must be POSITIVE, we can safely divide both sides of the inequality by \(c^6\) to get: \(a^3c>0\)

Finally, since \(a^2\) must be POSITIVE, we can safely divide both sides of the inequality by \(a^2\) to get: \(ac>0\)

So, the ONLY relevant conclusion we can make is that \(ac>0\)

Answer: C

Cheers,

Brent

_________________

Re: a^3b^4c^7>0
[#permalink]
16 Nov 2018, 18:20

1

Answer: C

A: if ab <0 then:

a<0 and b>0 : then c should be negative to have a^3*b^4*c^7 >0

a>0 and b<0 : then it’s ok because b’s power is even.

So A is possible but not obligatory.

B: it’s possible, But it’s not obligatory.

C: ac is positive: True

Because power of a and c are odd, they both should have same sign, both negative or positibve to have the whole expression positive.

_________________

A: if ab <0 then:

a<0 and b>0 : then c should be negative to have a^3*b^4*c^7 >0

a>0 and b<0 : then it’s ok because b’s power is even.

So A is possible but not obligatory.

B: it’s possible, But it’s not obligatory.

C: ac is positive: True

Because power of a and c are odd, they both should have same sign, both negative or positibve to have the whole expression positive.

_________________

Follow your heart

Re: a^3b^4c^7>0
[#permalink]
15 Jul 2019, 08:13

1

the above statement will be true if any of the following statement are true,

1. a , b , c are all positive numbers

2. if a is +ve, b is -ve and c is +ve

3. if a is -ve, b is +ve and c is -ve

Therefore only option C is always true

1. a , b , c are all positive numbers

2. if a is +ve, b is -ve and c is +ve

3. if a is -ve, b is +ve and c is -ve

Therefore only option C is always true

Re: a^3b^4c^7>0
[#permalink]
15 Jul 2019, 08:15

GreenlightTestPrep wrote:

Carcass wrote:

\(a^3b^4c^7>0\)

Which of the following statements must be true?

Indicate all such statements.

A. \(ab\) is negative

B. \(abc\) is positive

C. \(ac\) is positive

Which of the following statements must be true?

Indicate all such statements.

A. \(ab\) is negative

B. \(abc\) is positive

C. \(ac\) is positive

Key Concept: (any number)^(EVEN INTEGER) ≥ 0

First, since \(a^3b^4c^7>0\), we know that a ≠ 0, b ≠ 0, and c ≠ 0

Next, since \(b^4\) must be POSITIVE, we can safely divide both sides of the inequality by \(b^4\) to get: \(a^3c^7>0\)

Also, since \(c^6\) must be POSITIVE, we can safely divide both sides of the inequality by \(c^6\) to get: \(a^3c>0\)

Finally, since \(a^2\) must be POSITIVE, we can safely divide both sides of the inequality by \(a^2\) to get: \(ac>0\)

So, the ONLY relevant conclusion we can make is that \(ac>0\)

Answer: C

Cheers,

Brent

Re: a^3b^4c^7>0
[#permalink]
01 Sep 2019, 18:56

Fatemeh wrote:

Answer: C

A: if ab <0 then:

a<0 and b>0 : then c should be negative to have a^3*b^4*c^7 >0

a>0 and b<0 : then it’s ok because b’s power is even.

So A is possible but not obligatory.

B: it’s possible, But it’s not obligatory.

C: ac is positive: True

Because power of a and c are odd, they both should have same sign, both negative or positibve to have the whole expression positive.

A: if ab <0 then:

a<0 and b>0 : then c should be negative to have a^3*b^4*c^7 >0

a>0 and b<0 : then it’s ok because b’s power is even.

So A is possible but not obligatory.

B: it’s possible, But it’s not obligatory.

C: ac is positive: True

Because power of a and c are odd, they both should have same sign, both negative or positibve to have the whole expression positive.

nvm got it, got tricked

abc: - - + -> +

347: - + + -> -

Re: a^3b^4c^7>0
[#permalink]
02 Sep 2019, 06:08

2

Expert Reply

shadowmr20 wrote:

how come B isn't an answer?

We're told that \(a^3b^4c^7>0\)

So, it COULD be the case that \(a=1\), \(b=-1\) and \(c=1\)

Statement B says \(abc\) must be positive

However, if \(a=1\), \(b=-1\) and \(c=1\) then \(abc\) is negative

So, we can eliminate B

Cheers,

Brent

_________________

Re: a^3b^4c^7>0
[#permalink]
04 Sep 2019, 06:28

GreenlightTestPrep wrote:

shadowmr20 wrote:

how come B isn't an answer?

We're told that \(a^3b^4c^7>0\)

So, it COULD be the case that \(a=1\), \(b=-1\) and \(c=1\)

Statement B says \(abc\) must be positive

However, if \(a=1\), \(b=-1\) and \(c=1\) then \(abc\) is negative

So, we can eliminate B

Cheers,

Brent

if b is equal -1 then it must be positive as rules coz \(b^4\). If a or c is equal -1 not the b then we can easily eliminate the answer choice B.

_________________

New to the GRE, and GRE CLUB Forum?

GRE: All About GRE | Search GRE Specific Questions | Download Vault

Posting Rules: QUANTITATIVE | VERBAL

Questions' Banks and Collection:

ETS: ETS Free PowerPrep 1 & 2 All 320 Questions Explanation. | ETS All Official Guides

3rd Party Resource's: All In One Resource's | All Quant Questions Collection | All Verbal Questions Collection | Manhattan 5lb All Questions Collection

Books: All GRE Best Books

Scores: Average GRE Score Required By Universities in the USA

Tests: All Free & Paid Practice Tests | GRE Prep Club Tests

Extra: Permutations, and Combination

Vocab: GRE Vocabulary

Facebook GRE Prep Group: Click here to join FB GRE Prep Group

GRE: All About GRE | Search GRE Specific Questions | Download Vault

Posting Rules: QUANTITATIVE | VERBAL

Questions' Banks and Collection:

ETS: ETS Free PowerPrep 1 & 2 All 320 Questions Explanation. | ETS All Official Guides

3rd Party Resource's: All In One Resource's | All Quant Questions Collection | All Verbal Questions Collection | Manhattan 5lb All Questions Collection

Books: All GRE Best Books

Scores: Average GRE Score Required By Universities in the USA

Tests: All Free & Paid Practice Tests | GRE Prep Club Tests

Extra: Permutations, and Combination

Vocab: GRE Vocabulary

Facebook GRE Prep Group: Click here to join FB GRE Prep Group

Re: a^3b^4c^7>0
[#permalink]
30 May 2020, 18:13

Brent's answer is a really clever one, and a reminder that when you see inequalities like this on the GRE, you should look to manipulate it so that it's still true. You'll likely find a cool shortcut.

Re: a^3b^4c^7>0
[#permalink]
24 Jul 2021, 21:30

Hello from the GRE Prep Club BumpBot!

Thanks to another GRE Prep Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.

Thanks to another GRE Prep Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.

gmatclubot

Moderators:

Multiple-choice Questions — Select One or More Answer Choices |
||

## Hi Guest,Here are updates for you:## ANNOUNCEMENTSExperts’ YouTube and Chat Q&A This Week! 10 AM ET | 3 PM GMT | 7:30 PM IST Why your GMAT Score is NOT Improving? | How to Overcome GMAT Score Plateau? Sep/28 10:30 AM ET | 3:30 PM GMT | 8 PM IST How these MBA Candidates with Ordinary Profiles got into M7 BSchools? - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Sign up to get email reminders of your YouTube sessions SUBSCRIBE to GMAT Club’s YouTube Channel to Get Timely Reminders of Your Sessions Get Forum Quiz FREE for 7 Days (regardless of the free trial or other subscriptions) |