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.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 500,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

Concentration: Entrepreneurship, International Business

GMAT 1: 440 Q33 V13

GPA: 3

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

Show Tags

19 Mar 2013, 18:05

1

This post received 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

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

Show Tags

25 Jul 2013, 21:20

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 _____________________________________________________________________________

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

Show Tags

29 Aug 2013, 05:36

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!

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

Show Tags

15 Apr 2015, 00:21

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.
_________________

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

Show Tags

23 Aug 2017, 20:13

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)

I enjoyed solving this problem. After solving it, It was also a pleasure seeing it categorized as Medium and a 600 question.

---

Starting with the givens:

Given XY > 0 this given should be interpreted as Either both X and Y are positive or Negative. For the product of two like signs always yields a positive. Given YZ < 0 this given should be interpreted as either Y or Z as positive or negative. For the product of two different signs always yields a negative.

Considering the implications of the givens, this problem branches off in two directions: the first is Y is negative; therefore, X is negative and Z is positive. And the second, Both X and Y are positive, while Z is negative

This problem asks for a MUST solution, so our two branches need to overlap the same answer.

If X and Y = - Z = + then (A) (B) (E) is eliminated, leaving us with (C) and (D) as possible Answers

If X and Y = + Z = - then (B)(D)(E) is eliminated, leaving us with (A) and (C) as possible answers.

Since the only overlapping solution to our two branches is (C), (C) must be the answer

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)

SInce xy > 0:

x = pos and y = pos

OR

x = neg and y = neg

SInce yz < 0:

y = neg and z = pos

OR

y = pos and z = neg

Thus, we have two scenarios:

1) x = pos, y = pos, and z = neg

2) x = neg, y = neg, and z = pos

Since y^2 is always positive regardless of whether y is positive or negative, we see that the product of x and z will always be negative, and thus x(y^2)z will always be negative.

Answer: C
_________________

Jeffery Miller Head of GMAT Instruction

GMAT Quant Self-Study Course 500+ lessons 3000+ practice problems 800+ HD solutions

Version 8.1 of the WordPress for Android app is now available, with some great enhancements to publishing: background media uploading. Adding images to a post or page? Now...

Post today is short and sweet for my MBA batchmates! We survived Foundations term, and tomorrow's the start of our Term 1! I'm sharing my pre-MBA notes...

“Keep your head down, and work hard. Don’t attract any attention. You should be grateful to be here.” Why do we keep quiet? Being an immigrant is a constant...