inequalities

This topic has expert replies
Source: — Data Sufficiency |

User avatar
Legendary Member
Posts: 1309
Joined: Mon Apr 04, 2011 5:34 am
Location: India
Thanked: 310 times
Followed by:123 members
GMAT Score:750

by cans » Thu Jun 09, 2011 8:52 am
mv<pv<0
v>0??
a) m<p
mv<pv
(p-m)v>0
(p-m)>0
Thus v>0
Sufficent
b)m<0
mv<0
thus v>0
Sufficient
IMO D
If my post helped you- let me know by pushing the thanks button ;)

Contact me about long distance tutoring!
[email protected]

Cans!!

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 3835
Joined: Fri Apr 02, 2010 10:00 pm
Location: Milpitas, CA
Thanked: 1854 times
Followed by:523 members
GMAT Score:770

by Anurag@Gurome » Sat Jun 11, 2011 3:09 am
divya23 wrote:if mv<pv<0 is v>0
m<p
m<0
Statement 1: m < p --> (m - p) < 0 --> (m - p) is negative
From question stem, mv < pv --> (mv - pv) < 0 --> v(m - p) < 0
As product of v and (m - p) is negative and (m - p) is also negative, v must be positive.

Sufficient.

Statement 2: m < 0 --> m is negative
From question stem, mv < 0
As product of v and m is negative and m is also negative, v must be positive.

Sufficient.

The correct answer is D.
Anurag Mairal, Ph.D., MBA
GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
1-800-566-4043 (USA)

Join Our Facebook Groups
GMAT with Gurome
https://www.facebook.com/groups/272466352793633/
Admissions with Gurome
https://www.facebook.com/groups/461459690536574/
Career Advising with Gurome
https://www.facebook.com/groups/360435787349781/

Newbie | Next Rank: 10 Posts
Posts: 2
Joined: Thu Oct 15, 2009 4:18 am

by abasirov » Fri Aug 05, 2011 2:28 am
:(
Last edited by abasirov on Fri Aug 05, 2011 2:42 am, edited 1 time in total.

Master | Next Rank: 500 Posts
Posts: 298
Joined: Tue Feb 16, 2010 1:09 am
Thanked: 2 times
Followed by:1 members

by Deepthi Subbu » Fri Aug 05, 2011 2:38 am
Anurag@Gurome wrote:
divya23 wrote:if mv<pv<0 is v>0
m<p
m<0
Statement 1: m < p --> (m - p) < 0 --> (m - p) is negative
From question stem, mv < pv --> (mv - pv) < 0 --> v(m - p) < 0
As product of v and (m - p) is negative and (m - p) is also negative, v must be positive.

Sufficient.

Statement 2: m < 0 --> m is negative
From question stem, mv < 0
As product of v and m is negative and m is also negative, v must be positive.

Sufficient.

The correct answer is D.
Hi Anurag ,

As far as what i understand , for inequalities , if we are not aware of the sign of the variable , multiplication or division is not possible .

Can you please quantify on how you arrived at mv < pv from stem 1 . Are we not supposed to reverse the sign if 'v' has a different sign ?

Newbie | Next Rank: 10 Posts
Posts: 2
Joined: Thu Oct 15, 2009 4:18 am

by abasirov » Fri Aug 05, 2011 2:45 am
Hi Anurag

Please could you also explain how we got to this stage

Statement 1: m < p --> (m - p) < 0 --> (m - p) is negative

How can you -p away from both sides when we do not know the sign for p?
Thank you

Master | Next Rank: 500 Posts
Posts: 298
Joined: Tue Feb 16, 2010 1:09 am
Thanked: 2 times
Followed by:1 members

by Deepthi Subbu » Fri Aug 05, 2011 4:08 am
abasirov wrote:Hi Anurag

Please could you also explain how we got to this stage

Statement 1: m < p --> (m - p) < 0 --> (m - p) is negative

How can you -p away from both sides when we do not know the sign for p?
Thank you
Hi abasirov ,

I just understood the problem .

There's one rule that ul have to keep in mind for inequalities.
Rule - The sign of the inequality changes only during division or multiplication.

For eg : x + 1 < 2.

Here you are allowed to subtract -1 from both sides without a change in sign . So the equation becomes x + 1 - 1 < 2 - 1
x < 1 .

b . -x + 1 < 2

Following the same step as in ex 1 , we arive at -x < 1 . However we want the value of x , hence divide by -1 on both sides .This is where a sign change is mandated . The final equation becomes

x > -1 .

hope it helps.