Summer is Coming! Join the Game of Timers Competition to Win Epic Prizes. Registration is Open. Game starts Mon July 1st.

It is currently 20 Jul 2019, 15:32

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

M25-34

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

Hide Tags

Find Similar Topics 
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 56304
M25-34  [#permalink]

Show Tags

New post 16 Sep 2014, 01:24
3
28
00:00
A
B
C
D
E

Difficulty:

  95% (hard)

Question Stats:

27% (01:26) correct 73% (01:11) wrong based on 375 sessions

HideShow timer Statistics


Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 56304
Re M25-34  [#permalink]

Show Tags

New post 16 Sep 2014, 01:24
5
10
Official Solution:


Inequality \(x^7*y^2*z^3 \gt 0\) to be true \(x\) and \(z\) must be either both positive or both negative (in order \(x^7*z^3\) to be positive) AND \(y\) must not be zero (in order \(x^7*y^2*z^3\) not to equal to zero).

(1) \(yz \lt 0\). This statement implies that \(y \neq 0\). Don't know about \(x\) and \(z\). Not sufficient.

(2) \(xz \gt 0\). This statement implies that \(x\) and \(z\) are either both positive or both negative. Don't know about \(y\): if \(y=0\), then the expression is not positive it's equal 0 . Not sufficient.

Notice that if \(\)

(1)+(2) Sufficient.


Answer: C
_________________
Intern
Intern
avatar
Joined: 23 Oct 2014
Posts: 4
Re: M25-34  [#permalink]

Show Tags

New post 17 Nov 2014, 04:54
1
Bunuel wrote:
Official Solution:


Inequality \(x^7*y^2*z^3 \gt 0\) to be true \(x\) and \(z\) must be either both positive or both negative (in order \(x^7*z^3\) to be positive) AND \(y\) must not be zero (in order \(x^7*y^2*z^3\) not to equal to zero).

(1) \(yz \lt 0\). This statement implies that \(y \neq 0\). Don't know about \(x\) and \(z\). Not sufficient.

(2) \(xz \gt 0\). This statement implies that \(x\) and \(z\) are either both positive or both negative. Don't know about \(y\). Not sufficient.

(1)+(2) Sufficient.


Answer: C


Hi Bunuel, for (2) don't we know that y is always positive given it's raised to the power of 2 (and there's no imaginery numbers on the GMAT)?

Therefore, if y is always positive, then (2) is sufficient?
Intern
Intern
avatar
Joined: 25 Dec 2012
Posts: 16
GMAT ToolKit User
Re: M25-34  [#permalink]

Show Tags

New post 17 Nov 2014, 06:19
1
illusion10 wrote:
Bunuel wrote:
Official Solution:


Inequality \(x^7*y^2*z^3 \gt 0\) to be true \(x\) and \(z\) must be either both positive or both negative (in order \(x^7*z^3\) to be positive) AND \(y\) must not be zero (in order \(x^7*y^2*z^3\) not to equal to zero).

(1) \(yz \lt 0\). This statement implies that \(y \neq 0\). Don't know about \(x\) and \(z\). Not sufficient.

(2) \(xz \gt 0\). This statement implies that \(x\) and \(z\) are either both positive or both negative. Don't know about \(y\). Not sufficient.

(1)+(2) Sufficient.


Answer: C


Hi Bunuel, for (2) don't we know that y is always positive given it's raised to the power of 2 (and there's no imaginery numbers on the GMAT)?

Therefore, if y is always positive, then (2) is sufficient?


Yes I agree, I think the answer must be B, because with the information given the answer is always > 0
Manager
Manager
avatar
Joined: 17 Oct 2012
Posts: 61
Location: India
Concentration: Strategy, Finance
WE: Information Technology (Computer Software)
Re: M25-34  [#permalink]

Show Tags

New post 17 Nov 2014, 06:32
illusion10 wrote:
Bunuel wrote:
Official Solution:


Inequality \(x^7*y^2*z^3 \gt 0\) to be true \(x\) and \(z\) must be either both positive or both negative (in order \(x^7*z^3\) to be positive) AND \(y\) must not be zero (in order \(x^7*y^2*z^3\) not to equal to zero).

(1) \(yz \lt 0\). This statement implies that \(y \neq 0\). Don't know about \(x\) and \(z\). Not sufficient.

(2) \(xz \gt 0\). This statement implies that \(x\) and \(z\) are either both positive or both negative. Don't know about \(y\). Not sufficient.

(1)+(2) Sufficient.


Answer: C


Hi Bunuel, for (2) don't we know that y is always positive given it's raised to the power of 2 (and there's no imaginery numbers on the GMAT)?

Therefore, if y is always positive, then (2) is sufficient?



For statement (2), Y could be zero also, in that case \(x^7*y^2*z^3 \gt 0\) will not hold true.
Intern
Intern
avatar
Joined: 25 Dec 2012
Posts: 16
GMAT ToolKit User
Re: M25-34  [#permalink]

Show Tags

New post 17 Nov 2014, 06:35
gbascurs wrote:
illusion10 wrote:
Bunuel wrote:
Official Solution:


Inequality \(x^7*y^2*z^3 \gt 0\) to be true \(x\) and \(z\) must be either both positive or both negative (in order \(x^7*z^3\) to be positive) AND \(y\) must not be zero (in order \(x^7*y^2*z^3\) not to equal to zero).

(1) \(yz \lt 0\). This statement implies that \(y \neq 0\). Don't know about \(x\) and \(z\). Not sufficient.

(2) \(xz \gt 0\). This statement implies that \(x\) and \(z\) are either both positive or both negative. Don't know about \(y\). Not sufficient.

(1)+(2) Sufficient.


Answer: C


Hi Bunuel, for (2) don't we know that y is always positive given it's raised to the power of 2 (and there's no imaginery numbers on the GMAT)?

Therefore, if y is always positive, then (2) is sufficient?


Yes I agree, I think the answer must be B, because with the information given the answer is always > 0


I saw what is the problem with B, Y can be 0 or not.....
Intern
Intern
avatar
Joined: 23 Oct 2014
Posts: 4
Re: M25-34  [#permalink]

Show Tags

New post 19 Nov 2014, 03:51
1
chetan86 wrote:
illusion10 wrote:
Bunuel wrote:
Official Solution:


Inequality \(x^7*y^2*z^3 \gt 0\) to be true \(x\) and \(z\) must be either both positive or both negative (in order \(x^7*z^3\) to be positive) AND \(y\) must not be zero (in order \(x^7*y^2*z^3\) not to equal to zero).

(1) \(yz \lt 0\). This statement implies that \(y \neq 0\). Don't know about \(x\) and \(z\). Not sufficient.

(2) \(xz \gt 0\). This statement implies that \(x\) and \(z\) are either both positive or both negative. Don't know about \(y\). Not sufficient.

(1)+(2) Sufficient.


Answer: C


Hi Bunuel, for (2) don't we know that y is always positive given it's raised to the power of 2 (and there's no imaginery numbers on the GMAT)?

Therefore, if y is always positive, then (2) is sufficient?



For statement (2), Y could be zero also, in that case \(x^7*y^2*z^3 \gt 0\) will not hold true.


Thanks, definitely got caught out on that trap!
Intern
Intern
avatar
Joined: 12 Oct 2014
Posts: 1
GMAT ToolKit User
Re: M25-34  [#permalink]

Show Tags

New post 31 Dec 2014, 02:47
I think the answer should be B. Given that Y is squared, it can be inferred that the middle Y term is POSITIVE. If both X and Z are negative, it yields a final positive number. Likewise, if both X and Z are positive, it yields a final positive number as well.
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 56304
Re: M25-34  [#permalink]

Show Tags

New post 31 Dec 2014, 04:54
meisin123 wrote:
I think the answer should be B. Given that Y is squared, it can be inferred that the middle Y term is POSITIVE. If both X and Z are negative, it yields a final positive number. Likewise, if both X and Z are positive, it yields a final positive number as well.


Please read the whole thread before posting. Thank you.

y^2 is not positive, it's non-negative, so it CAN be 0.
_________________
Current Student
User avatar
Joined: 03 Aug 2011
Posts: 280
Concentration: Strategy, Finance
GMAT 1: 640 Q44 V34
GMAT 2: 700 Q42 V44
GMAT 3: 680 Q44 V39
GMAT 4: 740 Q49 V41
GPA: 3.7
WE: Project Management (Energy and Utilities)
GMAT ToolKit User Reviews Badge
Re: M25-34  [#permalink]

Show Tags

New post 15 Feb 2015, 05:08
2
I just love this kind of GMAT questions. They know after reading (A) you will assume you know what "y" is. Genious!
_________________
Thank you very much for reading this post till the end! Kudos?
Intern
Intern
User avatar
Joined: 15 Aug 2014
Posts: 7
GMAT 1: 640 Q47 V31
GMAT ToolKit User
Re: M25-34  [#permalink]

Show Tags

New post 09 Apr 2015, 07:26
I got this question in the GMATClub test and picked B as the answer. Should have considered y could also be zero.

Really nice question, thank you!
Manager
Manager
avatar
Joined: 28 Dec 2013
Posts: 68
Re M25-34  [#permalink]

Show Tags

New post 04 Nov 2015, 16:28
I think this is a high-quality question and the explanation isn't clear enough, please elaborate. There's not a clear explanation why c is sufficient can you please show with numbers ?
Senior Manager
Senior Manager
User avatar
Joined: 31 Mar 2016
Posts: 376
Location: India
Concentration: Operations, Finance
GMAT 1: 670 Q48 V34
GPA: 3.8
WE: Operations (Commercial Banking)
GMAT ToolKit User
Re M25-34  [#permalink]

Show Tags

New post 22 Aug 2016, 04:30
I think this is a high-quality question and I agree with explanation.
Intern
Intern
avatar
B
Joined: 12 Jan 2017
Posts: 34
Location: United States (NY)
Schools: Booth '21 (D)
GMAT 1: 710 Q47 V41
GPA: 3.48
Re: M25-34  [#permalink]

Show Tags

New post 13 Jul 2018, 07:09
Bunuel wrote:
Official Solution:


Inequality \(x^7*y^2*z^3 \gt 0\) to be true \(x\) and \(z\) must be either both positive or both negative (in order \(x^7*z^3\) to be positive) AND \(y\) must not be zero (in order \(x^7*y^2*z^3\) not to equal to zero).

(1) \(yz \lt 0\). This statement implies that \(y \neq 0\). Don't know about \(x\) and \(z\). Not sufficient.

(2) \(xz \gt 0\). This statement implies that \(x\) and \(z\) are either both positive or both negative. Don't know about \(y\): if \(y=0\), then the expression is not positive it's equal 0 . Not sufficient.

Notice that if \(\)

(1)+(2) Sufficient.


Answer: C


This is a super sneaky one because generally I think you'll see xyz =/= 0, whereas here it's not present and the test-taker will still assume it.
Intern
Intern
avatar
B
Joined: 16 Jun 2018
Posts: 38
Location: India
Schools: Stern '21
GMAT 1: 700 Q49 V41
GPA: 4
Reviews Badge
Re M25-34  [#permalink]

Show Tags

New post 11 Dec 2018, 11:18
I don't agree with the explanation. I think the answer should be B, because if at we consider the value of any of the variables x / y/ z as 0, then the question in itself will not hold true.
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 56304
Re: M25-34  [#permalink]

Show Tags

New post 11 Dec 2018, 21:39
Sheetal15 wrote:
I don't agree with the explanation. I think the answer should be B, because if at we consider the value of any of the variables x / y/ z as 0, then the question in itself will not hold true.


The correct answer is C. For (2) if y = 0, (which does NOT contradict the second statement) then the expression (x^7∗y^2∗z^3) will not positive it will be 0. This is explained couple of times above.
_________________
Director
Director
User avatar
P
Joined: 14 Feb 2017
Posts: 724
Location: Australia
Concentration: Technology, Strategy
GMAT 1: 560 Q41 V26
GMAT 2: 550 Q43 V23
GMAT 3: 650 Q47 V33
GPA: 2.61
WE: Management Consulting (Consulting)
CAT Tests
Re: M25-34  [#permalink]

Show Tags

New post 13 Jul 2019, 21:31
Its easy to see that if we know the signs of x and z we can determine whether the question is > 0, PROVIDED Y =/= 0

Y= 0 must be tested here.

Statement 1 indicates that Y cannot equal 0, but doesn't indicate the signs of x, therefore Insufficient

Statement 2 indicates that xz> 0, but we don't know if y=0.

If y=0 then (positive)*0^even exponent is not greater than 0
If y is not equal to zero than (positive)*(y)^even exponent > 0
I tripped on this mistake myself. Making a note for retention.
_________________
Goal: Q49, V41

+1 Kudos if you like my post pls!
GMAT Club Bot
Re: M25-34   [#permalink] 13 Jul 2019, 21:31
Display posts from previous: Sort by

M25-34

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

Moderators: chetan2u, Bunuel






Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne