GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 17 Jul 2018, 16:10

### 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

# Whether xy<1? 1). x + y = 1 2). x^2 + y^2 = 1

Author Message
Manager
Joined: 04 Sep 2006
Posts: 113
Whether xy<1? 1). x + y = 1 2). x^2 + y^2 = 1 [#permalink]

### Show Tags

27 Jun 2009, 22:17
00:00

Difficulty:

(N/A)

Question Stats:

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

### HideShow timer Statistics

Whether xy<1?
1). x + y = 1 2). x^2 + y^2 = 1

--== Message from GMAT Club Team ==--

This is not a quality discussion. It has been retired.

If you would like to discuss this question please re-post it in the respective forum. Thank you!

To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative | Verbal Please note - we may remove posts that do not follow our posting guidelines. Thank you.
Manager
Joined: 28 Jan 2004
Posts: 198
Location: India

### Show Tags

28 Jun 2009, 18:47
very good explanation. +1 to you.
Manager
Joined: 07 Apr 2009
Posts: 143

### Show Tags

19 Jul 2009, 05:08
IMO 'C'

Quote:
very good explanation. +1 to you.

I dont see any explanation !

I cant explain why B is not sufficient in itself.

COming to C

ya$$(x+y)^2 = x^2+y^2+2xy$$

substitute stmt1 & 2, we get xy = 0 , hence < 1
Retired Moderator
Joined: 05 Jul 2006
Posts: 1734

### Show Tags

19 Jul 2009, 10:12
vcbabu wrote:
Whether xy<1?
1). x + y = 1 2). x^2 + y^2 = 1

xy< 1 only if xy = fraction ,-ve or 0

from 1

x+y =1 we can tell that xy is not -ve but it could = 0 and we can't tell if xy is a fraction or not.......insuff

from 2

xy could be -ve or 0 or fraction but we can be sure.........insuff

both toegther

the only possible way for x+y =1 , x^2+y^2 = 1 is that one of the variables is 0 and the other is = 1

thus xy = 0 then C is the answer
Retired Moderator
Joined: 05 Jul 2006
Posts: 1734

### Show Tags

19 Jul 2009, 10:13
vcbabu wrote:
Whether xy<1?
1). x + y = 1 2). x^2 + y^2 = 1

xy< 1 only if xy = fraction ,-ve or 0

from 1

x+y =1 we can tell that xy is not -ve but it could = 0 and we can't tell if xy is a fraction or not.......insuff

from 2

xy could be -ve or 0 or fraction but we can be sure.........insuff

both toegther

the only possible way for x+y =1 , x^2+y^2 = 1 is that one of the variables is 0 and the other is = 1

thus xy = 0 then C is the answer
Manager
Joined: 04 Sep 2006
Posts: 113

### Show Tags

22 Jul 2009, 11:21
OA IS D.

By picking numbers , each is suff.
Senior Manager
Joined: 04 Jun 2008
Posts: 279

### Show Tags

22 Jul 2009, 11:33
vcbabu wrote:
Whether xy<1?
1). x + y = 1 2). x^2 + y^2 = 1

D is correct

xy< 1 only when
1) exactly one of x and y is negative
2) they are both fractions <1 (can be negative or positive)

stmt1: x+y cannot be equal to 1 if both are positive integers, or both are negative, or one is negative but other is a positive integer so that xy >1, So this confirms that x+y must be satisfying atleast one of the 2 conditions given above

stmt 2: Again x^2 + y+2 will never be =1 if both are positive/negative integers.
Manager
Joined: 07 Apr 2009
Posts: 143

### Show Tags

22 Jul 2009, 12:28
thanks for the explanation ! As I get more aquainted with DS I get more terrified

--== Message from GMAT Club Team ==--

This is not a quality discussion. It has been retired.

If you would like to discuss this question please re-post it in the respective forum. Thank you!

To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative | Verbal Please note - we may remove posts that do not follow our posting guidelines. Thank you.
Re: inequality   [#permalink] 22 Jul 2009, 12:28
Display posts from previous: Sort by

# Events & Promotions

 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®.