If xy > 0 and yz < 0, which of the following must be negativ : GMAT Problem Solving (PS)
Check GMAT Club Decision Tracker for the Latest School Decision Releases http://gmatclub.com/AppTrack

 It is currently 21 Jan 2017, 06:45

### 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 June
Open Detailed Calendar

# If xy > 0 and yz < 0, which of the following must be negativ

Author Message
TAGS:

### Hide Tags

Intern
Joined: 14 Jul 2012
Posts: 8
Concentration: Marketing, Entrepreneurship
WE: Sales (Other)
Followers: 0

Kudos [?]: 20 [0], given: 4

If xy > 0 and yz < 0, which of the following must be negativ [#permalink]

### Show Tags

19 Mar 2013, 11:42
7
This post was
BOOKMARKED
00:00

Difficulty:

35% (medium)

Question Stats:

64% (02:05) correct 36% (00:50) wrong based on 362 sessions

### HideShow timer Statistics

If xy > 0 and yz < 0, which of the following must be negative:

A. xyz
B. xy(z^2)
C. x(y^2)z
D. x(y^2)(z^2)
E. (x^2)(y^2)(z^2)
[Reveal] Spoiler: OA

Last edited by Bunuel on 19 Mar 2013, 11:54, edited 2 times in total.
Renamed the topic, edited the question and the tags.
Math Expert
Joined: 02 Sep 2009
Posts: 36590
Followers: 7090

Kudos [?]: 93318 [11] , given: 10557

Re: If xy > 0 and yz < 0, which of the following must be negativ [#permalink]

### Show Tags

19 Mar 2013, 11:57
11
KUDOS
Expert's post
4
This post was
BOOKMARKED
GMAThirst wrote:
If xy > 0 and yz < 0, which of the following must be negative:

A. xyz
B. xy(z^2)
C. x(y^2)z
D. x(y^2)(z^2)
E. (x^2)(y^2)(z^2)

Notice that option C is x(y^2)z = (xy)(yz) = positive*negative = negative.

_________________
Manager
Joined: 04 Oct 2011
Posts: 224
Location: India
GMAT 1: 440 Q33 V13
GMAT 2: 0 Q0 V0
GPA: 3
Followers: 0

Kudos [?]: 48 [1] , given: 44

Re: If xy > 0 and yz < 0, which of the following must be negativ [#permalink]

### Show Tags

19 Mar 2013, 17:05
1
KUDOS
GMAThirst wrote:
If xy > 0 and yz < 0, which of the following must be negative:

A. xyz
B. xy(z^2)
C. x(y^2)z
D. x(y^2)(z^2)
E. (x^2)(y^2)(z^2)

xy > 0
++ (or)
--
yz < 0
+- (or)
-+

Remember Square of any number is always +ve. so we can remove all squares

A. xyz there is a chance for --+ so may be +
B. xy ++ or --
C. xz if x is + then z should be - and vice versa
D. x may be + or -
E. +ve
_________________

GMAT - Practice, Patience, Persistence
Kudos if u like

Intern
Joined: 14 Jul 2012
Posts: 8
Concentration: Marketing, Entrepreneurship
WE: Sales (Other)
Followers: 0

Kudos [?]: 20 [0], given: 4

Re: If xy > 0 and yz < 0, which of the following must be negativ [#permalink]

### Show Tags

20 Mar 2013, 05:39
Hi, sorry to bother again, but I still didn't understand either of the explanations.....

I saw a long way in the book to solve it but I didn't get how both of you were able to solve it quick in that manner.

Thanks.
Math Expert
Joined: 02 Sep 2009
Posts: 36590
Followers: 7090

Kudos [?]: 93318 [1] , given: 10557

Re: If xy > 0 and yz < 0, which of the following must be negativ [#permalink]

### Show Tags

20 Mar 2013, 05:43
1
KUDOS
Expert's post
GMAThirst wrote:
Hi, sorry to bother again, but I still didn't understand either of the explanations.....

I saw a long way in the book to solve it but I didn't get how both of you were able to solve it quick in that manner.

Thanks.

xy > 0 means that xy is positive.
yz < 0 means that yz is negative.

x(y^2)z = (xy)(yz) = positive*negative = negative. Thus option C is always negative.

Hope it's clear.
_________________
Intern
Joined: 14 Jul 2012
Posts: 8
Concentration: Marketing, Entrepreneurship
WE: Sales (Other)
Followers: 0

Kudos [?]: 20 [0], given: 4

Re: If xy > 0 and yz < 0, which of the following must be negativ [#permalink]

### Show Tags

20 Mar 2013, 05:48
Hey Banuel,

Thanks it's much clearer now. Also, I'll make sure to follow the GMAT Rules for posting
Director
Joined: 03 Aug 2012
Posts: 916
Concentration: General Management, General Management
GMAT 1: 630 Q47 V29
GMAT 2: 680 Q50 V32
GPA: 3.7
WE: Information Technology (Investment Banking)
Followers: 23

Kudos [?]: 692 [0], given: 322

Re: If xy > 0 and yz < 0, which of the following must be negativ [#permalink]

### Show Tags

25 Jul 2013, 20:20
I follow the tables for these types of questions

XY>0 => Both must be -ve or both must be +ve.

YZ<0 =>Both must be of opposite signs.

X | Y | Z

+ + -
- - +

Evaluate all the options by this you will arrive at (C).

Rgds,
TGC !
_________________

Rgds,
TGC!
_____________________________________________________________________
I Assisted You => KUDOS Please
_____________________________________________________________________________

Intern
Joined: 06 Jan 2013
Posts: 11
Location: United States
Concentration: Finance, Economics
GMAT Date: 11-15-2013
GPA: 3.5
WE: Education (Education)
Followers: 0

Kudos [?]: 24 [0], given: 24

Re: If xy > 0 and yz < 0, which of the following must be negativ [#permalink]

### Show Tags

29 Aug 2013, 04:36
I also follow the table approach for these types of questions, as per the attached file. I set up the columns for x, y, and z, and check which combination of positive and negative values I need to satisfy the conditions given (xy>0 and yz<0), then I check each answer choice in turn. When actually doing these questions I wouldn't fill in the whole table (since the answer is C there is no point checking D and E), but for the sake of completeness I added them. Hope it helps a bit, I'm more visual so didn't either consider the algebraic approach given above!
Attachments

File comment: Solution table

Table.png [ 3.87 KiB | Viewed 4675 times ]

Current Student
Joined: 06 Sep 2013
Posts: 2035
Concentration: Finance
GMAT 1: 770 Q0 V
Followers: 62

Kudos [?]: 594 [0], given: 355

Re: If xy > 0 and yz < 0, which of the following must be negativ [#permalink]

### Show Tags

05 Jan 2014, 07:14
GMAThirst wrote:
If xy > 0 and yz < 0, which of the following must be negative:

A. xyz
B. xy(z^2)
C. x(y^2)z
D. x(y^2)(z^2)
E. (x^2)(y^2)(z^2)

If 'x' and 'y' have the same sign, and 'y' and 'z' have different signs, then it must follow that 'x' and 'z' have different sign

Hence y^2 will always be positive and x*z will always be negative

Thus C gives the correct answer

Cheers!
J
GMAT Club Legend
Joined: 09 Sep 2013
Posts: 13476
Followers: 576

Kudos [?]: 163 [0], given: 0

Re: If xy > 0 and yz < 0, which of the following must be negativ [#permalink]

### Show Tags

14 Apr 2015, 23:21
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.
_________________
Director
Joined: 07 Aug 2011
Posts: 581
GMAT 1: 630 Q49 V27
Followers: 3

Kudos [?]: 406 [0], given: 75

Re: If xy > 0 and yz < 0, which of the following must be negativ [#permalink]

### Show Tags

15 Apr 2015, 02:59
GMAThirst wrote:
If xy > 0 and yz < 0, which of the following must be negative:

A. xyz
B. xy(z^2)
C. x(y^2)z
D. x(y^2)(z^2)
E. (x^2)(y^2)(z^2)

from stem, x and y have same sign and z is just opposite to x and y .
clear C .
_________________

Thanks,
Lucky

_______________________________________________________
Kindly press the to appreciate my post !!

Senior Manager
Affiliations: Harvard University (Class of '02)
Joined: 10 Jul 2015
Posts: 310
GMAT 1: 770 Q47 V48
WE: Education (Education)
Followers: 45

Kudos [?]: 266 [0], given: 42

If xy > 0 and yz < 0, which of the following must be negativ [#permalink]

### Show Tags

05 May 2016, 17:30
Attached is a visual that should help.
Attachments

Screen Shot 2016-05-05 at 6.44.19 PM.png [ 141.98 KiB | Viewed 1283 times ]

_________________

Harvard grad and 770 GMAT scorer, offering high-quality private GMAT tutoring, both in-person and via Skype, since 2002.

McElroy Tutoring

If xy > 0 and yz < 0, which of the following must be negativ   [#permalink] 05 May 2016, 17:30
Similar topics Replies Last post
Similar
Topics:
30 If xy > 0 and yz < 0, which of the following must be negativ 11 27 Feb 2014, 06:02
16 If |x| = |y| and xy < 0, which of the following must be true 10 21 Dec 2013, 12:10
2 Given that xy > 0, which of the following must also be 4 09 Jul 2013, 09:23
3 If xyz < 0 and yz > 0, which of the following must be positi 4 20 Feb 2013, 15:41
7 If x^4*y < 0 and x*y^4 > 0 which of the following must be true? 5 02 Jul 2010, 22:42
Display posts from previous: Sort by