Are X and Y both positive?
1. 2X-2Y=1
2.X/Y >1
OA is c
Target Test Prep is 20% off right now!
Use code FLASH20
Available with Beat the GMAT members only code
MORE DETAILS
X, Y positive??
This topic has expert replies
-
sandeep1306
- Senior | Next Rank: 100 Posts
- Posts: 39
- Joined: Wed Jan 19, 2011 7:57 am
- Location: bangalore
-
pemdas
- Legendary Member
- Posts: 1085
- Joined: Fri Apr 15, 2011 2:33 pm
- Thanked: 158 times
- Followed by:21 members
st(1) when y=0 and x=1/2 And when x=1 and y=1/2 Not Sufficient;
st(2) either x<0 and y<0 {x=-1, y=-1/2) or x>0 and y>0 {x=1,y=1/2} Not Sufficient;
combined st(1&2): Sufficient, as x=1 and y=1/2 both are positive.
c
st(2) either x<0 and y<0 {x=-1, y=-1/2) or x>0 and y>0 {x=1,y=1/2} Not Sufficient;
combined st(1&2): Sufficient, as x=1 and y=1/2 both are positive.
c
sandeep1306 wrote:Are X and Y both positive?
1. 2X-2Y=1
2.X/Y >1
OA is c
Success doesn't come overnight!
-
srikanthb.69
- Junior | Next Rank: 30 Posts
- Posts: 12
- Joined: Wed Apr 13, 2011 6:37 am
- Thanked: 1 times
stmt 1 -> 2x-2y=1 => x-y=1/2 few values which satisfy this eq are
x=1,y=1/2 x=1/2,y=0 x= -1,y= -3/2 o x=1/4,y= -1/4 so Not Sufficient.
but From here we know that x>y
stmt 2 -> x/y>1 => x>y if x>0 & y>0 or x<y if x<0 & y<0 so Not sufficient.
From 1 we know that x>y and from 2 if x>y then x>0 & y>0 so answer is C
x=1,y=1/2 x=1/2,y=0 x= -1,y= -3/2 o x=1/4,y= -1/4 so Not Sufficient.
but From here we know that x>y
stmt 2 -> x/y>1 => x>y if x>0 & y>0 or x<y if x<0 & y<0 so Not sufficient.
From 1 we know that x>y and from 2 if x>y then x>0 & y>0 so answer is C
-
GMATGuruNY
- GMAT Instructor
- Posts: 15539
- Joined: Tue May 25, 2010 12:04 pm
- Location: New York, NY
- Thanked: 13060 times
- Followed by:1906 members
- GMAT Score:790
Statement 1: 2x-2y = 1.sandeep1306 wrote:Are X and Y both positive?
1. 2X-2Y=1
2.X/Y >1
OA is c
2(x-y) = 1
x-y = 1/2.
x = y + 1/2
x and y could both be positive: y = 1, x = 3/2.
x and y could both be negative: y = -1, x = -1/2.
Insufficient.
Statement 2: x/y > 1.
x and y could both be positive: x=2, y=1.
x and y could both be negative: x=-2, y=-1.
Insufficient.
Statements 1 and 2 combined: x = y + 1/2 and x/y > 1.
Plugging x = y + 1/2 into x/y > 1, we get:
(y + 1/2)/y > 1
y/y + y/2 > 1
1 + y/2 > 1
y/2 > 0
y > 0.
Since y is positive, and x = y + 1/2, we know that x is positive.
Sufficient.
The correct answer is C.
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.
As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.
For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.
As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.
For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3
GMAT/MBA Expert
-
Ian Stewart
- GMAT Instructor
- Posts: 2621
- Joined: Mon Jun 02, 2008 3:17 am
- Location: Montreal
- Thanked: 1090 times
- Followed by:355 members
- GMAT Score:780
From Statement 1, x = y + 1/2, which tells us nothing about the signs of x and y. We do, however, learn that x > y.sandeep1306 wrote:Are X and Y both positive?
1. 2X-2Y=1
2.X/Y >1
From Statement 2, we know that x and y share the same sign, but both could be negative or both could be positive.
With both statements, we know from Statement 1 that x > y. If y were negative, then we could divide by y on both sides (reversing the inequality) to find that x/y < 1. But we know from Statement 2 that is *not* true. So it's impossible for y to be negative, and y must be positive. Since x > y, x is also positive. C.
For online GMAT math tutoring, or to buy my higher-level Quant books and problem sets, contact me at ianstewartgmat at gmail.com
ianstewartgmat.com
ianstewartgmat.com
