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

 It is currently 16 Dec 2018, 02:56

### 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 December
PrevNext
SuMoTuWeThFrSa
2526272829301
2345678
9101112131415
16171819202122
23242526272829
303112345
Open Detailed Calendar
• ### FREE Quant Workshop by e-GMAT!

December 16, 2018

December 16, 2018

07:00 AM PST

09:00 AM PST

Get personalized insights on how to achieve your Target Quant Score.
• ### Free GMAT Prep Hour

December 16, 2018

December 16, 2018

03:00 PM EST

04:00 PM EST

Strategies and techniques for approaching featured GMAT topics

# If xy > 0, is xyz < 0?

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 51223
If xy > 0, is xyz < 0?  [#permalink]

### Show Tags

22 Apr 2016, 03:32
00:00

Difficulty:

35% (medium)

Question Stats:

70% (01:35) correct 30% (01:15) wrong based on 124 sessions

### HideShow timer Statistics

If xy > 0, is xyz < 0?

(1) xz > 0
(2) yz > 0

_________________
SC Moderator
Joined: 13 Apr 2015
Posts: 1687
Location: India
Concentration: Strategy, General Management
GMAT 1: 200 Q1 V1
GPA: 4
WE: Analyst (Retail)
Re: If xy > 0, is xyz < 0?  [#permalink]

### Show Tags

22 Apr 2016, 11:02
1
xy > 0 --> x and y have the same signs
Is xyz < 0?

St1: xz > 0 --> x and z have the same signs
Suppose x = +ve --> y = +ve and z = +ve --> Is xyz < 0? No
Suppose x = -ve --> y = -ve and z = -ve --> Is xyz < 0? Yes
Not Sufficient

St2: yz > 0 --> y and z have the same signs
Suppose y = +ve --> x = +ve and z = +ve --> Is xyz < 0? No
Suppose y = -ve --> x = -ve and z = -ve --> Is xyz < 0? Yes
Not Sufficient

Combining St1 and St2: xy > 0; xz > 0; yz > 0
x = +ve --> y = +ve and z = +ve
x = -ve --> y = -ve and z = -ve
Still not sufficient

Study Buddy Forum Moderator
Joined: 04 Sep 2016
Posts: 1269
Location: India
WE: Engineering (Other)
If xy > 0, is xyz < 0?  [#permalink]

### Show Tags

30 Aug 2018, 05:24

Quote:
If xy > 0, is xyz < 0?

(1) xz > 0
(2) yz > 0

Is it appropriate to combine two statements
as:
xy $$z^2$$ > 0

I incorrectly chose (C) here
_________________

It's the journey that brings us happiness not the destination.

PS Forum Moderator
Joined: 25 Feb 2013
Posts: 1217
Location: India
GPA: 3.82
Re: If xy > 0, is xyz < 0?  [#permalink]

### Show Tags

30 Aug 2018, 05:31
1

Quote:
If xy > 0, is xyz < 0?

(1) xz > 0
(2) yz > 0

Is it appropriate to combine two statements
as:
xy $$z^2$$ > 0

I incorrectly chose (C) here

Even if you combine the two statements you cannot arrive at xyz<0.

It is given that xy>0, so you simply need to know whether z<0 and on combining you will not get this information

Posted from my mobile device
Math Expert
Joined: 02 Aug 2009
Posts: 7108
Re: If xy > 0, is xyz < 0?  [#permalink]

### Show Tags

30 Aug 2018, 05:49
1

Quote:
If xy > 0, is xyz < 0?

(1) xz > 0
(2) yz > 0

Is it appropriate to combine two statements
as:
xy $$z^2$$ > 0

I incorrectly chose (C) here

So when you get xyz^2>0, it just tells you xy>0..
But if all three are negative..xyz^2 will be >0 but xyz<0..
However if all three are positive..xyz^2 will be >0 and xyz>0
_________________

1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html
3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html

GMAT online Tutor

Manager
Joined: 06 Nov 2016
Posts: 62
Location: Viet Nam
GPA: 3.54
Re: If xy > 0, is xyz < 0?  [#permalink]

### Show Tags

30 Aug 2018, 06:05
Bunuel wrote:
If xy > 0, is xyz < 0?

(1) xz > 0
(2) yz > 0

xy > 0 -> x and y have same signs

(1) xz > 0 -> x and z have same signs -> x, y, z have same signs. If all 3 variables are negative -> Yes. If all 3 variables are positive -> No. --> Not sufficient.
(2) yz > 0 -> y and z have same signs -> x, y, z have same signs. If all 3 variables are negative -> Yes. If all 3 variables are positive -> No. --> Not sufficient.
(1)+(2) x, y, z have same signs -> Not sufficient.

_________________
Re: If xy > 0, is xyz < 0? &nbs [#permalink] 30 Aug 2018, 06:05
Display posts from previous: Sort by

# If xy > 0, is xyz < 0?

 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®.