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

It is currently 17 Oct 2018, 14:24

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

M60-25

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

Hide Tags

Math Revolution GMAT Instructor
User avatar
V
Joined: 16 Aug 2015
Posts: 6375
GMAT 1: 760 Q51 V42
GPA: 3.82
Premium Member
M60-25  [#permalink]

Show Tags

New post 11 Jun 2018, 07:03
00:00
A
B
C
D
E

Difficulty:

(N/A)

Question Stats:

100% (00:11) correct 0% (00:00) wrong based on 1 sessions

HideShow timer Statistics

If \(x, y and z\) are positive numbers, is \(xy+z > x+yz\)?

1) \(x>1\)

2) \(y>1\)

_________________

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 $99 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
User avatar
V
Joined: 16 Aug 2015
Posts: 6375
GMAT 1: 760 Q51 V42
GPA: 3.82
Premium Member
Re M60-25  [#permalink]

Show Tags

New post 11 Jun 2018, 07:03
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.



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



Conditions 1) & 2):

\(xy + z > x + yz\)

⇔ \(xy - x - yz + z > 0\)

⇔ \(x(y-1)-z(y-1) > 0\)

⇔ \((x-z)(y-1) > 0\)

⇔ \(x - z > 0\) since \(y > 1\).



If \(x = 2, y = 2\), and \(z = 1\), then \(xy + z = 5, x + yz = 4\) and \(xy + z > x + yz\).

So, the answer is 'yes'.

If \(x = 2, y = 2\), and \(z = 3\), then \(xy + z = 7\), \(x + yz = 8\) and \(xy + z < x + yz\).

So, the answer is 'no'.

Since the question does not have a unique answer, both conditions together are not sufficient.



Therefore, E is the answer. 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: E
_________________

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 $99 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
Intern
avatar
Joined: 11 Nov 2013
Posts: 9
Re: M60-25  [#permalink]

Show Tags

New post 10 Aug 2018, 02:59
I think the scenario "If x = 2, y = 2 and z = 3 ..." is incorrect.

Since x – z > 0, x > z.
Intern
Intern
avatar
B
Joined: 01 Apr 2018
Posts: 6
Re: M60-25  [#permalink]

Show Tags

New post 14 Sep 2018, 07:30
Yes, the explanation is not Correct , if x - z >0 then how come x =2 and z=3? Please can someone help ?
Manager
Manager
avatar
S
Joined: 27 Aug 2014
Posts: 135
Concentration: Finance, Strategy
GPA: 3.9
WE: Analyst (Energy and Utilities)
CAT Tests
Re: M60-25  [#permalink]

Show Tags

New post 23 Sep 2018, 12:25
xy+z > x+yz
xy+z-x-yz>0
x(y-1)-z(y-1)>0
(x-z)(y-1)>0?

so for this statement to be true, (x-z) and (y-1) should have the same sign. We need to statements if they provide this info.

from 1: x>1, no info on y and z, so insuff
from 2: y>1, (y-1)>0, we don't have info on (x-z) so insuff


1+2 combined, x>1 and y-1>0, no info on x-z sp insuff. therefore E
GMAT Club Bot
Re: M60-25 &nbs [#permalink] 23 Sep 2018, 12:25
Display posts from previous: Sort by

M60-25

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

Moderators: chetan2u, Bunuel



cron
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®.