It is currently 12 Dec 2017, 05:28

Close

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.

Close

Request Expert Reply

Confirm Cancel

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

Is |x^7|*y^3*z^4>0

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

Hide Tags

Expert Post
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 42559

Kudos [?]: 135331 [0], given: 12687

Is |x^7|*y^3*z^4>0 [#permalink]

Show Tags

New post 02 Feb 2015, 07:21
Expert's post
4
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  35% (medium)

Question Stats:

66% (01:20) correct 34% (00:46) wrong based on 176 sessions

HideShow timer Statistics

Kudos [?]: 135331 [0], given: 12687

Expert Post
1 KUDOS received
Math Expert
User avatar
D
Joined: 02 Aug 2009
Posts: 5339

Kudos [?]: 6103 [1], given: 121

Re: Is |x^7|*y^3*z^4>0 [#permalink]

Show Tags

New post 02 Feb 2015, 08:23
1
This post received
KUDOS
Expert's post
ans E..
to know the ans, we require to know whether y is -ive..
1) it just tells us x and y are opposite in sign,... insufficient
2) it just tells us that y and z are of same sign.. insufficient
combined still insufficient
_________________

Absolute modulus :http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html

Kudos [?]: 6103 [1], given: 121

1 KUDOS received
Senior Manager
Senior Manager
User avatar
Joined: 28 Feb 2014
Posts: 295

Kudos [?]: 144 [1], given: 133

Location: United States
Concentration: Strategy, General Management
Reviews Badge
Re: Is |x^7|*y^3*z^4>0 [#permalink]

Show Tags

New post 02 Feb 2015, 10:46
1
This post received
KUDOS
Bunuel wrote:
Is |x^7|*y^3*z^4>0

(1) xy < 0
(2) yz > 0

Kudos for a correct solution.


|x^7|*y^3*z^4>0?

|x^7| will always be positive due to the absolute value
z^4 will always be positive due to the even power
y^3 could be negative (a 'no' to the question) or positive (a 'yes' to the question)

Rephrased, we are looking to see if y is positive or negative.
Is y positive or negative?

Statement 1:
x is negative and y is negative OR
x is positive and y is positive
Insufficient

Statement 2:
y is negative and z is negative OR
y is positive and z is positive
Insufficient

Combined, y could be positive or negative. Still insufficient to answer the question.

Answer: E

Kudos [?]: 144 [1], given: 133

1 KUDOS received
Manager
Manager
avatar
Joined: 17 Dec 2013
Posts: 60

Kudos [?]: 26 [1], given: 35

GMAT Date: 01-08-2015
GMAT ToolKit User
Re: Is |x^7|*y^3*z^4>0 [#permalink]

Show Tags

New post 02 Feb 2015, 13:38
1
This post received
KUDOS
Quote:
Is |x^7|*y^3*z^4>0

(1) xy < 0
(2) yz > 0


(1) -> either x or y is negative. since we only need to know if y is negative we do not get straight answer. insuff
(2) -> either both are negative or both are positive. since we only need to know if y is negative, we do not get a straight answer. insuff

(1/2) we got no new info. insuff.

-> E

Kudos [?]: 26 [1], given: 35

Expert Post
1 KUDOS received
EMPOWERgmat Instructor
User avatar
P
Status: GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 10364

Kudos [?]: 3678 [1], given: 173

Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: 340 Q170 V170
Re: Is |x^7|*y^3*z^4>0 [#permalink]

Show Tags

New post 02 Feb 2015, 18:19
1
This post received
KUDOS
Expert's post
Hi All,

It looks like everyone who's responded so far is comfortable using Number Properties to get to the correct answer. Any question that can be solved with Number Properties can also be solved by TESTing VALUES.

We're asked if |X^7|(Y^3)(Z^4) > 0. This is a YES/NO question.

Fact 1: XY < 0

This tells us that we have 1 POSITIVE and 1 NEGATIVE variable

IF....
X = 1
Y = -1
Z = 1
|1^7|[(-1)^3](1^4) = (1)(-1)(1) = -1 and the answer to the question is NO.

IF....
X = -1
Y = 1
Z = 1
|(-1)^7](1^3)(1^4) = (1)(1)(1) = 1 and the answer to the question is YES.
Fact 1 is INSUFFICIENT

Fact 2: YZ > 0

This tells us that either BOTH are positive OR BOTH are negative

IF....
X = -1
Y = 1
Z = 1
(from above), the answer to the question is YES.

IF...
X = 1
Y = -1
Z = -1
|1^7|[(-1)^3][(-1)^4] = (1)(-1)(1) = -1 and the answer to the question is NO.
Fact 2 is INSUFFICIENT

Combined, we know...
XY < 0
YZ > 0

We can use our prior work (from Fact 2) to quickly deal with this last step:

IF....
X = -1
Y = 1
Z = 1
(from above), the answer to the question is YES.

IF...
X = 1
Y = -1
Z = -1
(from above) and the answer to the question is NO.
Combined, INSUFFICIENT

Final Answer:
[Reveal] Spoiler:
E


GMAT assassins aren't born, they're made,
Rich
_________________

760+: Learn What GMAT Assassins Do to Score at the Highest Levels
Contact Rich at: Rich.C@empowergmat.com

Rich Cohen

Co-Founder & GMAT Assassin

Special Offer: Save $75 + GMAT Club Tests Free
  Official GMAT Exam Packs + 70 Pt. Improvement Guarantee
www.empowergmat.com/

***********************Select EMPOWERgmat Courses now include ALL 6 Official GMAC CATs!***********************

Kudos [?]: 3678 [1], given: 173

1 KUDOS received
Manager
Manager
avatar
B
Joined: 02 Sep 2014
Posts: 89

Kudos [?]: 252 [1], given: 32

Location: United States
Schools: Haas EWMBA '20
GMAT 1: 770 Q50 V44
GPA: 3.97
GMAT ToolKit User Reviews Badge
Re: Is |x^7|*y^3*z^4>0 [#permalink]

Show Tags

New post 03 Feb 2015, 00:12
1
This post received
KUDOS
Bunuel wrote:
Is |x^7|*y^3*z^4>0

(1) xy < 0
(2) yz > 0

Kudos for a correct solution.


I have been burnt in these type of questions for NOT considering one of the numbers being = 0 so now I always start with thinking if one of them CAN be zero! :|
Anyway here we really need to know the sign of y AND if either one of x y or z are =0.

1) xy<0 here z can or cannot be zero. INSUFFICIENT
2) yz>0 here again x can or cannot be zero. INSUFFICIENT

Combining we know neither x y or z are zero. But together we cannot know the sign of y since it can be either sign and satisfy the requirements. So both together are also INSUFFICIENT.

Answer E.

Press kudos if you think I am right.

Kudos [?]: 252 [1], given: 32

Expert Post
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 42559

Kudos [?]: 135331 [0], given: 12687

Re: Is |x^7|*y^3*z^4>0 [#permalink]

Show Tags

New post 09 Feb 2015, 04:24
Bunuel wrote:
Is |x^7|*y^3*z^4>0

(1) xy < 0
(2) yz > 0

Kudos for a correct solution.


VERITAS PREP OFFICIAL SOLUTION:

E. Since neither the absolute value of x^7 nor the value of z^4 can be negative, the positive/negative value of |x^7|y^3z^4 will depend on the positive/negative value of y itself. (Note: the other possibility is that one of the terms could equal 0, but as you'll see with the statements that gets ruled out here)

For statement 1, xy < 0 means that either x or y (but not both) is negative. Since this means that y could be positive or y could be negative, this is not sufficient.

For statement 2, yz > 0 means that either y and z are both negative or y and z are both positive. Again, since this allows for both a positive and negative value of y, this is not sufficient.

Combining the statements, you should see that both a positive and a negative possibility both remain for y, so even together the statements are not sufficient. The correct answer is E.
_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics

Kudos [?]: 135331 [0], given: 12687

Non-Human User
User avatar
Joined: 09 Sep 2013
Posts: 14900

Kudos [?]: 287 [0], given: 0

Premium Member
Re: Is |x^7|*y^3*z^4>0 [#permalink]

Show Tags

New post 15 Aug 2017, 06:55
Hello from the GMAT Club BumpBot!

Thanks to another GMAT 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.
_________________

GMAT Books | GMAT Club Tests | Best Prices on GMAT Courses | GMAT Mobile App | Math Resources | Verbal Resources

Kudos [?]: 287 [0], given: 0

Re: Is |x^7|*y^3*z^4>0   [#permalink] 15 Aug 2017, 06:55
Display posts from previous: Sort by

Is |x^7|*y^3*z^4>0

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


GMAT Club MBA Forum Home| About| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

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®.