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

 It is currently 20 Mar 2019, 16:36 ### 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

#### Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here. ### Request Expert Reply # M60-13

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

### Hide Tags

Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 7096
GMAT 1: 760 Q51 V42 GPA: 3.82

### Show Tags 00:00

Difficulty:   25% (medium)

Question Stats: 53% (00:55) correct 47% (00:05) wrong based on 15 sessions

### HideShow timer Statistics

Is $$x|y|=xz?$$

1) $$x$$, $$y$$, and $$z$$ are positive

2) $$y^2=z^2$$

_________________ 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.
"Only $149 for 3 month Online Course" "Free Resources-30 day online access & Diagnostic Test" "Unlimited Access to over 120 free video lessons - try it yourself" Math Revolution GMAT Instructor V Joined: 16 Aug 2015 Posts: 7096 GMAT 1: 760 Q51 V42 GPA: 3.82 Re M60-13 [#permalink] ### Show Tags Official Solution: 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. "Only$149 for 3 month Online Course"
"Free Resources-30 day online access & Diagnostic Test"
"Unlimited Access to over 120 free video lessons - try it yourself"

Intern  B
Joined: 24 Oct 2015
Posts: 19
Location: Bahrain

### Show Tags

Condition 2) tells us that y=z or y=−z

In both the above possibilities, we can sufficiently answer that x |y| = xz ; because the modulus on y will ensure that both z and -z gives out a positive figure.

Why is it that we need the first condition?
Intern  B
Joined: 18 May 2017
Posts: 2

### Show Tags

ShivaniD wrote:
Condition 2) tells us that y=z or y=−z

In both the above possibilities, we can sufficiently answer that x |y| = xz ; because the modulus on y will ensure that both z and -z gives out a positive figure.

Why is it that we need the first condition?

I agree with you. I believe the answer they provided is wrong. This is not the first time REVOLUTION posted a wrong answer.
Intern  B
Joined: 04 Aug 2018
Posts: 6

### Show Tags

1
XIYI =XZ?

Break Down:- IYI = Z (canceling out x)
i.e. Z must be positive. (as IYI is always positive)
So one need to verify that Z is +ve as well as it is equal to Y in magnitude

1) The statement says that Z is +ve . But doesn't tell about magnitude of Z.
Hence Insufficient.

2)The statement says that Z can be + ve OR -ve . But magnitude of Z will be equal to that of Y.
Hence Insufficient.

Combining 1 & 2 , both conditions are satisfied. (Z is +ve as well as it is equal to Y in magnitude)
Intern  Joined: 18 Nov 2014
Posts: 12

### Show Tags Re M60-13   [#permalink] 18 Jan 2019, 12:23
Display posts from previous: Sort by

# M60-13

 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 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®.  