Last visit was: 24 Apr 2026, 15:39 It is currently 24 Apr 2026, 15:39
Home
Messages
Tests
Schools
Events
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.
Go to My Error Log Learn more
Close
Request Expert Reply
Confirm Cancel
User avatar
n2739178
User avatar
Joined: 12 May 2010
Last visit: 05 Jul 2013
Posts: 233
Own Kudos:
131
Given Kudos: 12
Location: United Kingdom
Concentration: Entrepreneurship, Technology
Schools: LBS '14 Oxford '14 Judge Sloan '14 INSEAD '14
GMAT Date: 10-22-2011
GPA: 3
WE:Information Technology (Internet and New Media)
Schools: LBS '14 Oxford '14 Judge Sloan '14 INSEAD '14
Posts: 233
Kudos: 131
why can't I divide by |y| ? 31 Oct 2011, 15:21
Kudos
Add Kudos
Bookmarks
Bookmark this Post
I don't understand why I can't divide by |y| here when rephrasing... can anyone help?

This is an MGMAT CAT question... They say this -->

"It is extremely tempting to divide both sides of this inequality by y or by the |y|, to come up with a rephrased question of “is x > y?” However, we do not know the sign of y, so this cannot be done. "

I thought you COULD divide y^2 by |y|, because |y| is positive?



Archived Topic
Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Where to now? Join ongoing discussions on thousands of quality questions in our Quantitative Questions Forum
Still interested in this question? Check out the "Best Topics" block below for a better discussion on this exact question, as well as several more related questions.
Thank you for understanding, and happy exploring!
User avatar
KarishmaB
User avatar
Joined: 16 Oct 2010
Last visit: 23 Apr 2026
Posts: 16,442
Own Kudos:
79,404
Given Kudos: 485
Location: Pune, India
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 16,442
Kudos: 79,404
why can't I divide by |y| ? 31 Oct 2011, 20:09
Kudos
Add Kudos
Bookmarks
Bookmark this Post
n2739178
I don't understand why I can't divide by |y| here when rephrasing... can anyone help?

This is an MGMAT CAT question... They say this -->

"It is extremely tempting to divide both sides of this inequality by y or by the |y|, to come up with a rephrased question of “is x > y?” However, we do not know the sign of y, so this cannot be done. "

I thought you COULD divide y^2 by |y|, because |y| is positive?
Show more

Yes, you can divide by |y| since it is positive. I think all they are trying to say is that you cannot rephrase the question as "Is x > y"

If you divide by |y|, you will get "Is \(x > y*\frac{y}{|y|}\)?"
You have to keep in mind that y/|y| can be 1 or -1 depending on whether y is positive or negative.
User avatar
fluke
User avatar
Retired Moderator
Joined: 20 Dec 2010
Last visit: 24 Oct 2013
Posts: 1,095
Own Kudos:
5,168
Given Kudos: 376
Posts: 1,095
Kudos: 5,168
why can't I divide by |y| ? 01 Nov 2011, 02:41
Kudos
Add Kudos
Bookmarks
Bookmark this Post
n2739178
I don't understand why I can't divide by |y| here when rephrasing... can anyone help?

This is an MGMAT CAT question... They say this -->

"It is extremely tempting to divide both sides of this inequality by y or by the |y|, to come up with a rephrased question of “is x > y?” However, we do not know the sign of y, so this cannot be done. "

I thought you COULD divide y^2 by |y|, because |y| is positive?
Show more

|y| can be 0 as well. Division by 0 is undefined.
User avatar
KarishmaB
User avatar
Joined: 16 Oct 2010
Last visit: 23 Apr 2026
Posts: 16,442
Own Kudos:
79,404
Given Kudos: 485
Location: Pune, India
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 16,442
Kudos: 79,404
why can't I divide by |y| ? 01 Nov 2011, 04:05
Kudos
Add Kudos
Bookmarks
Bookmark this Post
fluke

|y| can be 0 as well. Division by 0 is undefined.
Show more

Yes, you are right. Division by 0 is undefined. But its relevance in this question is very limited since statement 2 states that y > 0. You know that the two statements never conflict so you don't really need to worry about y = 0.

Even if this condition were not mentioned, instead of wondering whether x*|y| > y^2, I would find it far easier to work with x > y*y/|y| since the variables are separated here. I can separately worry about the condition "y=0" if it is possible in a particular question.

My question will be: Is \(x > y*y/|y|\)?

I will think, "y/|y| can be 1 or -1 (assuming y is not 0)"
Statement 1 says x > y. Then can I say that x > -y too (in case y/|y| = -1)? Not necessarily. If y is negative, it may not hold.
e.g. x = 3, y = -4
y/|y| = -1
x is greater than y but x (=3) is not greater than y*y/|y| (=4)
I don't really need to worry about y = 0 here.

Statement 2 clarifies that y is positive. Now we know that y/|y| = 1
Since statement 1 says x > y, it is sufficient to say x > y*y/|y|.
User avatar
n2739178
User avatar
Joined: 12 May 2010
Last visit: 05 Jul 2013
Posts: 233
Own Kudos:
131
Given Kudos: 12
Location: United Kingdom
Concentration: Entrepreneurship, Technology
Schools: LBS '14 Oxford '14 Judge Sloan '14 INSEAD '14
GMAT Date: 10-22-2011
GPA: 3
WE:Information Technology (Internet and New Media)
Schools: LBS '14 Oxford '14 Judge Sloan '14 INSEAD '14
Posts: 233
Kudos: 131
why can't I divide by |y| ? 03 Nov 2011, 13:48
Kudos
Add Kudos
Bookmarks
Bookmark this Post
great thanks guys!



Archived Topic
Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Where to now? Join ongoing discussions on thousands of quality questions in our Quantitative Questions Forum
Still interested in this question? Check out the "Best Topics" block above for a better discussion on this exact question, as well as several more related questions.
Thank you for understanding, and happy exploring!