BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

+?

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
User avatar
GMAT Instructor
Posts: 3650
Joined: Wed Jan 21, 2009 4:27 am
Location: India
Thanked: 267 times
Followed by:80 members
GMAT Score:760

+?

by sanju09 » Mon Apr 12, 2010 1:58 am
Is x + y positive?

(1) x - y is positive.

(2) y - x is negative.
The mind is everything. What you think you become. -Lord Buddha



Sanjeev K Saxena
Quantitative Instructor
The Princeton Review - Manya Abroad
Lucknow-226001

www.manyagroup.com
Top
Source: — Data Sufficiency |
Legendary Member
Posts: 2326
Joined: Mon Jul 28, 2008 3:54 am
Thanked: 173 times
Followed by:2 members
GMAT Score:710

by gmatmachoman » Mon Apr 12, 2010 2:24 am
sanju09 wrote:Is x + y positive?

(1) x - y is positive.

(2) y - x is negative.
IMO E
Top
Senior | Next Rank: 100 Posts
Posts: 65
Joined: Wed Nov 25, 2009 6:33 pm
Thanked: 3 times

by dxgamez » Mon Apr 12, 2010 2:34 am
Qn: is x + y > 0?

1. x - y > 0

X = 1, y = 1 suffice

x = 1, y = -1 insuffice

2. Same can be applied so insuffice. Identical to 1.

If one statement is insuffice, thus both are insufficient.

Choose E.

Can anyone advise if we can add the 2 inequalities instead of picking numbers?
Top
User avatar
GMAT Instructor
Posts: 3650
Joined: Wed Jan 21, 2009 4:27 am
Location: India
Thanked: 267 times
Followed by:80 members
GMAT Score:760

by sanju09 » Mon Apr 12, 2010 2:42 am
dxgamez wrote:Qn: is x + y > 0?

1. x - y > 0

X = 1, y = 1 suffice

x = 1, y = -1 insuffice

2. Same can be applied so insuffice. Identical to 1.

If one statement is insuffice, thus both are insufficient.

Choose E.

Can anyone advise if we can add the 2 inequalities instead of picking numbers?
You neither need to add inequalities nor to pick numbers here. Apply the basic number properties to get any credit in the given case. The number picking policy used in your explanation is even not clear to me. You didn't mention why it's so that "If one statement is insuffice, thus both are insufficient."
The mind is everything. What you think you become. -Lord Buddha



Sanjeev K Saxena
Quantitative Instructor
The Princeton Review - Manya Abroad
Lucknow-226001

www.manyagroup.com
Top
Senior | Next Rank: 100 Posts
Posts: 65
Joined: Wed Nov 25, 2009 6:33 pm
Thanked: 3 times

by dxgamez » Mon Apr 12, 2010 4:51 am
Sorry about the unclear explanation. Happens when you try to do everything in your mobile :)

Let me re-explain:-

st 1:- x - y > 0

Pick some numbers that satisfy st 1:-

x= 2, y = 1 ---- this shows that x+y is +ve, thus suffice cos qn stem is asking if x+y >0.

x = 1, y = -1 ---- this shows that x+y is equal to 0, thus insuffice cos doesnt satisfy qn stem.

thus, st 1 is insufficient.

st 2:- y-x < 0

multiplying (-) both sides gives x - y > 0, which is the same expression as st 1, thus insufficient.

@sanju09, you mentioned that "You neither need to add inequalities nor to pick numbers here. Apply the basic number properties to get any credit.."

could you show how to apply the basic number properties?

This is my thinking:-

1. simplify qn stem x > - y

2. st 1 & st 2 show that x > y

3. thus insufficient...

is this right?
Top
User avatar
GMAT Instructor
Posts: 3650
Joined: Wed Jan 21, 2009 4:27 am
Location: India
Thanked: 267 times
Followed by:80 members
GMAT Score:760

by sanju09 » Mon Apr 12, 2010 5:06 am
Both statements are same.

When x - y > 0, x > y, or x and y are different valued numbers whose sum could be anything, positive, negative, or zero. Hence, each of the identical statement is insufficient.

[spoiler]E[/spoiler]
The mind is everything. What you think you become. -Lord Buddha



Sanjeev K Saxena
Quantitative Instructor
The Princeton Review - Manya Abroad
Lucknow-226001

www.manyagroup.com
Top
Junior | Next Rank: 30 Posts
Posts: 12
Joined: Thu Mar 11, 2010 9:49 am
Thanked: 1 times

by Cdawg » Mon Apr 12, 2010 9:21 am
Inequalities:

(1) x-y > 0

(2) y-x < 0 =!= 0 < x-y OR x-y > 0

as sanju09 said, they are the same

test:
x=1 y=-2 => 1-(-2)=3, thus statements hold, and x+y=-1 (neg)
but statements also hold when x=2 y=1, and X+y=3 (pos)

thus you can't say whether they are + or -
ANSWER: E
Top
Post new topic Post Reply
• Page 1 of 1