numbers : from GMAT prep

This topic has expert replies
Newbie | Next Rank: 10 Posts
Posts: 6
Joined: Sun Mar 20, 2011 8:44 am
Thanked: 1 times

numbers : from GMAT prep

by prithviforever » Fri Jun 10, 2011 10:41 am
if -2x > 3y ,is x negative?
1. y>0
2. 2x+5y-20=0

Legendary Member
Posts: 1448
Joined: Tue May 17, 2011 9:55 am
Location: India
Thanked: 375 times
Followed by:53 members

by Frankenstein » Fri Jun 10, 2011 10:47 am
Hi,
-2x>3y
From(1):y>0. So -2x which is greater than 3y is also greater than 0
So, x is negative.
Sufficient

From(2): -2x = 5y-20
As -2x>3y, 5y-20>3y =>y>10. As y is positive, x should be negative
Sufficient

Hence, D
Cheers!

Things are not what they appear to be... nor are they otherwise

User avatar
Master | Next Rank: 500 Posts
Posts: 436
Joined: Tue Feb 08, 2011 3:07 am
Thanked: 72 times
Followed by:6 members

by manpsingh87 » Fri Jun 10, 2011 10:50 am
prithviforever wrote:if -2x > 3y ,is x negative?
1. y>0
2. 2x+5y-20=0
1) y>0;
multiplying 3 on both sides we have;
3y>0;

for -2x to become greater than 3y; x must be negative; because positive quantity is always greater than negative quantity, hence x must be negative, hence 1 alone is sufficient to answer the question.

2) 2x+5y=20;

also -2x>3y can be written as; 3y+2x<0;
2x+3y=20-2y;
now since 3y+2x<0; i.e. left hand side is negative therefore rhs must also be negative;
i.e. 20-2y<0;
20<2y;
10<y;since y>10; i.e. y is positive and greater than 10, therefore inequality will hold true only if x is negative,, hence 2 alone is also sufficient to answer this question..!!!

hence answer should be D
O Excellence... my search for you is on... you can be far.. but not beyond my reach!

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 » Fri Jun 10, 2011 9:43 pm
if -2x > 3y ,is x negative?
1. y>0
2. 2x+5y-20=0
a)y>0 thus 3y>0
also -2x>3y>0
thus x<0
Sufficient
b)2x+3y<0
y<-2x/3
5y<-10x/3
2x+5y-20<-4x/3-20
4x/3 + 20 <0
x<-15
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 2:56 am
prithviforever wrote:if -2x > 3y ,is x negative?
1. y>0
2. 2x+5y-20=0
Statement 1: y > 0
Hence, 3y > 0 --> -2x > 0 --> x < 0

Sufficient

Statement 2: 2x + 5y - 20 = 0
Hence, y = (20 - 2x)/5
Now, -2x > 3y --> -2x > 3*(20 - 2x)/5
--> -10x > 60 - 6x
--> 4x < -60
--> x < -15

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/