It is currently 20 Nov 2017, 00:58

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# Is x>y^2? (1) x>y+5 (2) x^2-y^2=0

Author Message
VP
Joined: 18 May 2008
Posts: 1258

Kudos [?]: 541 [0], given: 0

Is x>y^2? (1) x>y+5 (2) x^2-y^2=0 [#permalink]

### Show Tags

11 Feb 2009, 04:30
00:00

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions

### HideShow timer Statistics

This topic is locked. If you want to discuss this question please re-post it in the respective forum.

Is $$x>y^2?$$

(1) $$x>y+5$$
(2) $$x^2-y^2=0$$

Kudos [?]: 541 [0], given: 0

SVP
Joined: 07 Nov 2007
Posts: 1790

Kudos [?]: 1088 [0], given: 5

Location: New York

### Show Tags

11 Feb 2009, 04:48
ritula wrote:
Is $$x>y^2?$$

(1) $$x>y+5$$
(2) $$x^2-y^2=0$$

1)
y=-15 x= -5 x>y^2? No
y=-5 x = 1 x>y^2? Yes
Not sufficient
2)

x=-y= 2 2>4 No
x=-y=1/2 1/2>1/4 Yes

Not sufficient

combined

x>y+5 --> x-y>5

x^2-Y^2 = (x-y)(x+y)=0

x-y>5 --> x=-y
-> 2x>5 -->x>2.5

clearly x>y^2 ---> No for all values.

Sufficient

C
_________________

Smiling wins more friends than frowning

Kudos [?]: 1088 [0], given: 5

Senior Manager
Joined: 30 Nov 2008
Posts: 483

Kudos [?]: 367 [0], given: 15

Schools: Fuqua

### Show Tags

11 Feb 2009, 13:14
IMO C.

From clue 1 -

x > y + 5 ==> x - y > 5

Pick some intelligent numbers that satisfy this clue (In this case I try to pick the (x, y) combinations as (+,+), (+,-), (-,+), (-,-). Even if any two combinations result in the Question stem with two different ans, I ignore the clue. If all these combinations result in only one ans, then I check for the fractions between (-1,0) and (0,1) for x and y.

(x,y) = (7,1). Satifies clue 1. Substitue back in x > y^2 ==. 7 > 1 Yes.
(x,y) = (-1,-7). Satifies clue 1.Substitue back in x > y^2 ==. 1 > 49 No.

Two different ans. Hence the clue is insufficient.

From clue 2 -

x^2 - y^2 = 0 ==> x^2 = y^2. Coming back to the the question stem, x > y^2, it is same as "Is x > x^2". for any value of x where x< 0 or x > 1, x is always less than x^2. ie x > y^2 is No. But if we take a number between 0 and 1 for ex, x = 0.5, x > x^2 is true. Again we got two solutions. Hence the clue is insufficient.

Combine both the clues -

x - y > 5
x^2 - y^2 = 0 ==> (x+y)(x-y) = 0 From clue 1 we know that x-y <> 0 ==> x+y = 0 ==. y = -x.
Now substitute y back in x-y>5 ==> x-(-x) > 5 ==. 2x > 5 ==> x > 5/2 ==> x > 1.

We already know for x > 1, x <= x^2. Hence the question "Is x > y^2" can be answered as No. Sufficient.

Kudos [?]: 367 [0], given: 15

Re: DS   [#permalink] 11 Feb 2009, 13:14
Display posts from previous: Sort by

# Is x>y^2? (1) x>y+5 (2) x^2-y^2=0

 Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.