Q: If x>0, is x>y
(1) 5x-4y=3
(2) 4y-5x=3
OA is C
But for me: (2) => y=(3+5x)/4 which shows that y > x
x>0 => 5x+3>5x => (5x+3)/4>5x/4>x, y=(5x+3)/4>x => (2) is sufficient => B
HELP! The book is definitely wrong on this one.
This topic has expert replies
-
- Newbie | Next Rank: 10 Posts
- Posts: 4
- Joined: Sun May 30, 2010 11:50 pm
- Stuart@KaplanGMAT
- GMAT Instructor
- Posts: 3225
- Joined: Tue Jan 08, 2008 2:40 pm
- Location: Toronto
- Thanked: 1710 times
- Followed by:614 members
- GMAT Score:800
Here's another way to show that (2) is sufficient alone:thaipq5290 wrote:Q: If x>0, is x>y
(1) 5x-4y=3
(2) 4y-5x=3
OA is C
But for me: (2) => y=(3+5x)/4 which shows that y > x
x>0 => 5x+3>5x => (5x+3)/4>5x/4>x, y=(5x+3)/4>x => (2) is sufficient => B
4y - 5x = 3
4y = 5x + 3
y = (5/4)x + 3/4
Since x is positive, (5/4)x is greater than x. So:
y = (bigger than x) + 3/4
which is definitely bigger than x.
Stuart Kovinsky | Kaplan GMAT Faculty | Toronto
Kaplan Exclusive: The Official Test Day Experience | Ready to Take a Free Practice Test? | Kaplan/Beat the GMAT Member Discount
BTG100 for $100 off a full course