It is currently 22 Feb 2018, 22:55

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

Events & Promotions in June
Open Detailed Calendar

Is x|y|=xz?

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

Hide Tags

Expert Post
Math Revolution GMAT Instructor
User avatar
D
Joined: 16 Aug 2015
Posts: 4904
GPA: 3.82
Is x|y|=xz? [#permalink]

Show Tags

New post 24 Jan 2018, 00:28
Expert's post
1
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  45% (medium)

Question Stats:

55% (00:35) correct 45% (00:46) wrong based on 69 sessions

HideShow timer Statistics

[GMAT math practice question]

Is \(x|y|=xz?\)

1) \(x, y,\) and \(z\) are positive
2) \(y^2=z^2\)
[Reveal] Spoiler: OA

_________________

MathRevolution: Finish GMAT Quant Section with 10 minutes to spare
The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy.
Find a 10% off coupon code for GMAT Club members.
“Receive 5 Math Questions & Solutions Daily”
Unlimited Access to over 120 free video lessons - try it yourself
See our Youtube demo

Senior Manager
Senior Manager
User avatar
G
Joined: 17 Oct 2016
Posts: 327
Location: India
Concentration: Operations, Strategy
GPA: 3.73
WE: Design (Real Estate)
GMAT ToolKit User Premium Member CAT Tests
Re: Is x|y|=xz? [#permalink]

Show Tags

New post 24 Jan 2018, 00:45
C.

From Q stem we can decide |y|=z?

Statement 1 don't gives much info. in sufficient.

Statement 2 says y²=z².

At first it may look like this is sufficient. But not.

Lets say y=-1 and z=1, this satisfies Q stem as well as st2. But when y=1 and z=-1 Q stem is not satisfied; only st2 is satisfied. Hence st2 is not sufficient alone.

Combining, we get, y=1 and z=1 always (although the sign of y doesn't matter). Hence sufficient.

This is a Good 'Answer-B trap question'.
_________________

Help with kudos if u found the post useful. Thanks

Expert Post
Math Expert
User avatar
D
Joined: 02 Aug 2009
Posts: 5660
Re: Is x|y|=xz? [#permalink]

Show Tags

New post 24 Jan 2018, 01:41
MathRevolution wrote:
[GMAT math practice question]

Is \(x|y|=xz?\)

1) \(x, y,\) and \(z\) are positive
2) \(y^2=z^2\)



What do we get from x|y|=xz..
Is x=0 or |y|=z ?.. Sasindran you have missed out on x=0..

1) x,y and z are positive.
So \(x\neq{0}\),
but y can be z, Ans will be yes
And if y is NOT EQUAL to z, Ans is NO
Insuff
2)y^2=z^2...
If z is positive, Ans is yes
If z is NEGATIVE, and is NO
Insufficient..

Combined z is positive and equal to z..
Ans is yes
Sufficient

C
_________________

Absolute modulus :http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html


BANGALORE/-

Intern
Intern
avatar
B
Joined: 01 Nov 2017
Posts: 11
CAT Tests
Is x|y|=xz? [#permalink]

Show Tags

New post 24 Jan 2018, 02:35
Additional info for statement 2:

x^2=z^2 can be re-written as x^2-z^2=(x+z)(x-z)=0

Now it becomes clear, that there are 2 possible solutions, so we need to check for additional information in statement 1
Expert Post
Math Revolution GMAT Instructor
User avatar
D
Joined: 16 Aug 2015
Posts: 4904
GPA: 3.82
Re: Is x|y|=xz? [#permalink]

Show Tags

New post 26 Jan 2018, 00:16
=>

Forget conventional ways of solving math questions. For DS problems, the VA (Variable Approach) method is the quickest and easiest way to find the answer without actually solving the problem. Remember that equal numbers of variables and independent equations ensure a solution.

The first step of the VA (Variable Approach) method is to modify the original condition and the question, and then recheck the question.

Modifying the question:
\(x|y| = xz\)
\(⇔ x(|y|-z) = 0\)
\(⇔ x = 0\) or \(|y| = z\)
\(⇔ x = 0\) or \(y = z\) or \(y = -z\)

Since we have 3 variables (\(x, y,\) and \(z\)) and 0 equations, E is most likely to be the answer. So, we should consider conditions 1) & 2) together first.

Conditions 1) & 2):

Condition 2) tells us that \(y = z\)or \(y = -z\).
Since condition 1) states that \(x, y, z > 0\), we can only have \(y = z\).
Thus, both conditions are sufficient, when taken together.

Therefore, the answer is C.

In cases where 3 or more additional equations are required, such as for original conditions with “3 variables”, or “4 variables and 1 equation”, or “5 variables and 2 equations”, conditions 1) and 2) usually supply only one additional equation. Therefore, there is an 80% chance that E is the answer, a 15% chance that C is the answer, and a 5% chance that the answer is A, B or D. Since E (i.e. conditions 1) & 2) are NOT sufficient, when taken together) is most likely to be the answer, it is generally most efficient to begin by checking the sufficiency of conditions 1) and 2), when taken together. Obviously, there may be occasions on which the answer is A, B, C or D.
Answer: C
_________________

MathRevolution: Finish GMAT Quant Section with 10 minutes to spare
The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy.
Find a 10% off coupon code for GMAT Club members.
“Receive 5 Math Questions & Solutions Daily”
Unlimited Access to over 120 free video lessons - try it yourself
See our Youtube demo

Re: Is x|y|=xz?   [#permalink] 26 Jan 2018, 00:16
Display posts from previous: Sort by

Is x|y|=xz?

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


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