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

It is currently 17 Jan 2019, 15:34

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 in January
PrevNext
SuMoTuWeThFrSa
303112345
6789101112
13141516171819
20212223242526
272829303112
Open Detailed Calendar
  • The winning strategy for a high GRE score

     January 17, 2019

     January 17, 2019

     08:00 AM PST

     09:00 AM PST

    Learn the winning strategy for a high GRE score — what do people who reach a high score do differently? We're going to share insights, tips and strategies from data we've collected from over 50,000 students who used examPAL.
  • Free GMAT Strategy Webinar

     January 19, 2019

     January 19, 2019

     07:00 AM PST

     09:00 AM PST

    Aiming to score 760+? Attend this FREE session to learn how to Define your GMAT Strategy, Create your Study Plan and Master the Core Skills to excel on the GMAT.

what is the value of xyz?

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

Hide Tags

 
Intern
Intern
avatar
Joined: 29 Sep 2013
Posts: 47
What is the value of xyz?  [#permalink]

Show Tags

New post 26 Dec 2013, 09:45
1
3
00:00
A
B
C
D
E

Difficulty:

  45% (medium)

Question Stats:

58% (01:16) correct 42% (01:16) wrong based on 112 sessions

HideShow timer Statistics

What is the value of xyz?

(1) xyz - xy = 0
(2) Either x = 0, or y = 0 or z = 1


The see the OA, I think it's incorrect. What's your opinion?
Magoosh GMAT Instructor
User avatar
G
Joined: 28 Dec 2011
Posts: 4486
Re: What is the Value of xyz?  [#permalink]

Show Tags

New post 26 Dec 2013, 09:57
2
1
suk1234 wrote:
What is the value of\(xyz\)?

1) \(xyz - xy = 0\)
2) Either \(x=0,\) or \(y=0\) or \(z=1\)

The see the OA, I think it's incorrect. What's your opinion?

Dear suk1234,
I'm happy to respond. :-)

I think the OA of (E) is correct. First of all, Statement #1 and Statement #2 are logical equivalent, and one implies the other.
If x = 0 or y = 0, then the other could equal anything, z could equal anything, and the product would be zero.
If z = 1, then x & y could equal anything, and the product could equal any value on the continuous infinity of the number line.
Thus, there's no way to determine a definitive value of the product.

Does this make sense? Please let me know if you have any further questions.
Mike :-)
_________________

Mike McGarry
Magoosh Test Prep


Education is not the filling of a pail, but the lighting of a fire. — William Butler Yeats (1865 – 1939)

Intern
Intern
avatar
Joined: 29 Sep 2013
Posts: 47
Re: What is the Value of xyz?  [#permalink]

Show Tags

New post 26 Dec 2013, 10:11
mikemcgarry wrote:
suk1234 wrote:
What is the value of\(xyz\)?

1) \(xyz - xy = 0\)
2) Either \(x=0,\) or \(y=0\) or \(z=1\)

The see the OA, I think it's incorrect. What's your opinion?

Dear suk1234,
I'm happy to respond. :-)

I think the OA of (E) is correct. First of all, Statement #1 and Statement #2 are logical equivalent, and one implies the other.
If x = 0 or y = 0, then the other could equal anything, z could equal anything, and the product would be zero.
If z = 1, then x & y could equal anything, and the product could equal any value on the continuous infinity of the number line.
Thus, there's no way to determine a definitive value of the product.

Does this make sense? Please let me know if you have any further questions.
Mike :-)


Thank you Mike for the Quick rescue!

Here is how I evaluated Statement 1:

Z=1 and Either X=0 or Y=0 or Both X and Y = 0

Then evaluate all the possible values!
1. (X=0) 0*Y*1=0
2. (Y=0) X*0*1=0
3. (X and Y = 0) 0*0*1=0

I think in case of statement 2 this reasoning doesn't apply because it presents three cases which may or may not be true ( \(x=0,\) or \(y=0\) or \(z=1\) either of these can happen or not).
But in case of statement 1 we are definitely sure about the value of XY.
Magoosh GMAT Instructor
User avatar
G
Joined: 28 Dec 2011
Posts: 4486
Re: What is the Value of xyz?  [#permalink]

Show Tags

New post 26 Dec 2013, 14:14
1
1
suk1234 wrote:
Thank you Mike for the Quick rescue!

Here is how I evaluated Statement 1:

Z=1 and Either X=0 or Y=0 or Both X and Y = 0

Then evaluate all the possible values!
1. (X=0) 0*Y*1=0
2. (Y=0) X*0*1=0
3. (X and Y = 0) 0*0*1=0

I think in case of statement 2 this reasoning doesn't apply because it presents three cases which may or may not be true ( \(x=0,\) or \(y=0\) or \(z=1\) either of these can happen or not).
But in case of statement 1 we are definitely sure about the value of XY.

Dear suk1234
I'm happy to respond. :-)

Statement #1 says
xyz - xy = 0
Add xy to both sides:
xyz = xy
(xy)*z = (xy)

Here, we are presented with a choice.
Case One:
If (xy) does not equal zero, then we can divide by (xy), and get z = 1. That's one case, in which (xy) can have any value on the number line other than zero, and z = 1. Here, the product xyz would be equal to xy, and could be anything other than zero.
Case Two:
If (xy) = 0, then z could be anything on the number line. This is the other case. If (xy) = 0, then either x = 0 or y = 0, which will make the product equal zero. (Here, z could be 1, or it could be anything else on the number line.)

You see, the crucial mathematical word is the word "or" ---- either z = 1 OR (xy) = 0. You are interpreting the two requirements as if they are simultaneous, not a mutually exclusive choice. The two cases are actually mutually exclusive.

Does all this make sense?
Mike :-)
_________________

Mike McGarry
Magoosh Test Prep


Education is not the filling of a pail, but the lighting of a fire. — William Butler Yeats (1865 – 1939)

Intern
Intern
avatar
Joined: 29 Sep 2013
Posts: 47
Re: What is the Value of xyz?  [#permalink]

Show Tags

New post 27 Dec 2013, 00:48
mikemcgarry wrote:
suk1234 wrote:
Thank you Mike for the Quick rescue!

Here is how I evaluated Statement 1:

Z=1 and Either X=0 or Y=0 or Both X and Y = 0

Then evaluate all the possible values!
1. (X=0) 0*Y*1=0
2. (Y=0) X*0*1=0
3. (X and Y = 0) 0*0*1=0

I think in case of statement 2 this reasoning doesn't apply because it presents three cases which may or may not be true ( \(x=0,\) or \(y=0\) or \(z=1\) either of these can happen or not).
But in case of statement 1 we are definitely sure about the value of XY.

Dear suk1234
I'm happy to respond. :-)

Statement #1 says
xyz - xy = 0
Add xy to both sides:
xyz = xy
(xy)*z = (xy)

Here, we are presented with a choice.
Case One:
If (xy) does not equal zero, then we can divide by (xy), and get z = 1. That's one case, in which (xy) can have any value on the number line other than zero, and z = 1. Here, the product xyz would be equal to xy, and could be anything other than zero.
Case Two:
If (xy) = 0, then z could be anything on the number line. This is the other case. If (xy) = 0, then either x = 0 or y = 0, which will make the product equal zero. (Here, z could be 1, or it could be anything else on the number line.)

You see, the crucial mathematical word is the word "or" ---- either z = 1 OR (xy) = 0. You are interpreting the two requirements as if they are simultaneous, not a mutually exclusive choice. The two cases are actually mutually exclusive.

Does all this make sense?
Mike :-)

Oh I see, where I was going wrong with it.Thank Mike that was an amazing explanation.
Director
Director
User avatar
G
Joined: 23 Jan 2013
Posts: 559
Schools: Cambridge'16
Re: What is the value of xyz?  [#permalink]

Show Tags

New post 08 Mar 2016, 03:41
xyz=?

St.1 xyz-xy=0 => xy(z-1)=0, so xy=0 or z=1 or both . If xy=0, xyz=0, if z=1, not clear. INSUFF.

St.2 Either x = 0, or y = 0 or z = 1. Again if z=1, not clear. INSUFF.

St1+St2 tell the same, so INSUFF

E
Manager
Manager
avatar
Joined: 17 Oct 2012
Posts: 65
Location: India
Concentration: Strategy, Finance
WE: Information Technology (Computer Software)
what is the value of xyz?  [#permalink]

Show Tags

New post Updated on: 08 May 2016, 20:30
what is the value of xyz?
(1) xyz-xy=0
(2) Either x=0 or y=0 or z=1

Originally posted by chetan86 on 08 May 2016, 20:08.
Last edited by chetan86 on 08 May 2016, 20:30, edited 1 time in total.
Math Expert
User avatar
V
Joined: 02 Aug 2009
Posts: 7198
what is the value of xyz?  [#permalink]

Show Tags

New post 08 May 2016, 20:16
chetan86 wrote:
what is the value of xyz?
(1) xyz-xy=0
(2) Either x=0 or y=0



Hi,
you will have to relook into OA or the typo erros ..

(1) \(xyz-xy=0\)..
\(xy(z-1) = 0...\)
either z=1 or xy = 0...
if z=1 and xy is NOT equal to 0.. xyz can be any non-zero integer depending on xy..
If xy =0, ans will be 0..
Insuff

(2) Either x=0 or y=0
In any case , xyz will be 0..
Suff

B..

NOTE - Pl Check before posting and post correctly.
Merging topics
_________________

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
Manager
avatar
Joined: 17 Oct 2012
Posts: 65
Location: India
Concentration: Strategy, Finance
WE: Information Technology (Computer Software)
Re: what is the value of xyz?  [#permalink]

Show Tags

New post 08 May 2016, 20:23
Yeah, I rechecked the answer, and it is E. Even I am confused about this question so thought to post this question to clear my understandings.
This question is from Advance GMAT Quant.

OE is :
We can test different numeric scenarios for x, y and z using Scenario Charts. Statement (1) tells us that xyz – xy = 0. First, let's factor the equation:
xyz – xy = 0
xy(z – 1) = 0
For this product to equal zero, either x = 0, or y = 0, or z = 1.

Thus if x = 0 or y = 0, then xyz = 0, but if z = 1, then xyz could take on any value. INSUFFICIENT.

Statement (2) tells us that either x = 0 or y = 0 or z = 1. This is the exact same information from Statement (1), so we can eliminate A, B and C by Spotting Identical Statements. Since Statement (1) also proved to be insufficient, we can eliminate D as well.

The correct answer is E.

chetan2u wrote:
chetan86 wrote:
what is the value of xyz?
(1) xyz-xy=0
(2) Either x=0 or y=0



Hi,
you will have to relook into OA or the typo erros ..

(1) \(xyz-xy=0\)..
\(xy(z-1) = 0...\)
either z=1 or xy = 0...
if z=1 and xy is NOT equal to 0.. xyz can be any non-zero integer depending on xy..
If xy =0, ans will be 0..
Insuff

(2) Either x=0 or y=0
In any case , xyz will be 0..
Suff

B..
Math Expert
User avatar
V
Joined: 02 Aug 2009
Posts: 7198
Re: what is the value of xyz?  [#permalink]

Show Tags

New post 08 May 2016, 20:27
chetan86 wrote:
Yeah, I rechecked the answer, and it is E. Even I am confused about this question so thought to post this question to clear my understandings.
This question is from Advance GMAT Quant.

OE is :
We can test different numeric scenarios for x, y and z using Scenario Charts. Statement (1) tells us that xyz – xy = 0. First, let's factor the equation:
xyz – xy = 0
xy(z – 1) = 0
For this product to equal zero, either x = 0, or y = 0, or z = 1.

Thus if x = 0 or y = 0, then xyz = 0, but if z = 1, then xyz could take on any value. INSUFFICIENT.

Statement (2) tells us that either x = 0 or y = 0 or z = 1. This is the exact same information from Statement (1), so we can eliminate A, B and C by Spotting Identical Statements. Since Statement (1) also proved to be insufficient, we can eliminate D as well.

The correct answer is E.

chetan2u wrote:
chetan86 wrote:
what is the value of xyz?
(1) xyz-xy=0
(2) Either x=0 or y=0



Hi,
you will have to relook into OA or the typo erros ..

(1) \(xyz-xy=0\)..
\(xy(z-1) = 0...\)
either z=1 or xy = 0...
if z=1 and xy is NOT equal to 0.. xyz can be any non-zero integer depending on xy..
If xy =0, ans will be 0..
Insuff

(2) Either x=0 or y=0
In any case , xyz will be 0..
Suff

B..


Then there is a error in what you have given as statement 2 and what is mentioned..
as per your Q.. II is "Either x=0 or y=0", whereas the source is giveing in the OE as "Statement (2) tells us that either x = 0 or y = 0 or z = 1"..

Both the statements do NOT mean the same ..
and if statement is - Statement (2) tells us that either x = 0 or y = 0 or z = 1.. ANS will be E
_________________

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
Manager
avatar
Joined: 17 Oct 2012
Posts: 65
Location: India
Concentration: Strategy, Finance
WE: Information Technology (Computer Software)
what is the value of xyz?  [#permalink]

Show Tags

New post 08 May 2016, 20:30
chetan2u wrote:

Then there is a error in what you have given as statement 2 and what is mentioned..
as per your Q.. II is "Either x=0 or y=0", whereas the source is giveing in the OE as "Statement (2) tells us that either x = 0 or y = 0 or z = 1"..

Both the statements do NOT mean the same ..
and if statement is - Statement (2) tells us that either x = 0 or y = 0 or z = 1.. ANS will be E


I have updated the question. Thanks!!
Manager
Manager
avatar
Joined: 13 Apr 2016
Posts: 59
Location: India
GMAT 1: 640 Q50 V27
GPA: 3
WE: Operations (Hospitality and Tourism)
Re: what is the value of xyz?  [#permalink]

Show Tags

New post 08 May 2016, 21:05
[quote="chetan86"]what is the value of xyz?
(1) xyz-xy=0
(2) Either x=0 or y=0 or z=1

I think the answer has to be E because none of the statement is giving any fix value for any of the variable and also by combining we are not getting any confirmed answer.
Manager
Manager
avatar
Joined: 17 Oct 2012
Posts: 65
Location: India
Concentration: Strategy, Finance
WE: Information Technology (Computer Software)
Re: what is the value of xyz?  [#permalink]

Show Tags

New post 09 May 2016, 03:52
Below explanation resolved my doubts. Thanks!!

mikemcgarry wrote:
suk1234 wrote:
Thank you Mike for the Quick rescue!

Here is how I evaluated Statement 1:

Z=1 and Either X=0 or Y=0 or Both X and Y = 0

Then evaluate all the possible values!
1. (X=0) 0*Y*1=0
2. (Y=0) X*0*1=0
3. (X and Y = 0) 0*0*1=0

I think in case of statement 2 this reasoning doesn't apply because it presents three cases which may or may not be true ( \(x=0,\) or \(y=0\) or \(z=1\) either of these can happen or not).
But in case of statement 1 we are definitely sure about the value of XY.

Dear suk1234
I'm happy to respond. :-)

Statement #1 says
xyz - xy = 0
Add xy to both sides:
xyz = xy
(xy)*z = (xy)

Here, we are presented with a choice.
Case One:
If (xy) does not equal zero, then we can divide by (xy), and get z = 1. That's one case, in which (xy) can have any value on the number line other than zero, and z = 1. Here, the product xyz would be equal to xy, and could be anything other than zero.
Case Two:
If (xy) = 0, then z could be anything on the number line. This is the other case. If (xy) = 0, then either x = 0 or y = 0, which will make the product equal zero. (Here, z could be 1, or it could be anything else on the number line.)

You see, the crucial mathematical word is the word "or" ---- either z = 1 OR (xy) = 0. You are interpreting the two requirements as if they are simultaneous, not a mutually exclusive choice. The two cases are actually mutually exclusive.

Does all this make sense?
Mike :-)
Non-Human User
User avatar
Joined: 09 Sep 2013
Posts: 9419
Premium Member
Re: what is the value of xyz?  [#permalink]

Show Tags

New post 24 Mar 2018, 21:30
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

GMAT Club Bot
Re: what is the value of xyz? &nbs [#permalink] 24 Mar 2018, 21:30
Display posts from previous: Sort by

what is the value of xyz?

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


Copyright

GMAT Club MBA Forum Home| About| Terms and Conditions and Privacy Policy| 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®.