NEW HERE? LEARN MORE
closeclose
Last visit was: 26 Apr 2024, 07:30 It is currently 26 Apr 2024, 07:30
Decision Tracker
My Rewards
New posts
New comers' posts

Close
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
Your Progress

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
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Go to My Error Log Learn more
Close
Request Expert Reply
Confirm Cancel

are x , y > 0 ? 1) 2x-2y =1 2) x/y > 1 should we

User avatar
abhaypratapsingh
Manager
Manager
Joined: 21 Mar 2006
Posts: 107
Own Kudos [?]: 104 [0]
Given Kudos: 0
Send PM
are x , y > 0 ? 1) 2x-2y =1 2) x/y > 1 should we [#permalink] New post   19 Jul 2008, 22:58
00:00
A
B
C
D
E

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 1 sessions
Hide Show timer Statistics
are x , y > 0 ?

1) 2x-2y =1
2) x/y > 1

should we always solve DS q's with taking sample numbers ? this q's is prety tricky if I try to solve the eqn , ineq.



Archived Topic
Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Where to now? Join ongoing discussions on thousands of quality questions in our Data Sufficiency (DS) Forum
Still interested in this question? Check out the "Best Topics" block below for a better discussion on this exact question, as well as several more related questions.
Thank you for understanding, and happy exploring!
User avatar
abhijit_sen
Senior Manager
Senior Manager
Joined: 10 Sep 2007
Posts: 458
Own Kudos [?]: 938 [1]
Given Kudos: 0
 Q50  V34
Send PM
Re: are x , y > 0 ? 1) 2x-2y =1 2) x/y > 1 should we [#permalink] New post   19 Jul 2008, 23:08
1
Kudos
1) Tells us 2x-2y =1. This tells us definitely that x > y however both x and y can greater, eqaul to or less than 0. So A and D out.

2) x/y > 1
This tells us x > y if y is +ve (which means x is +ve as well) Or x < y is y is -ve (which means x is -ve as well). Again two possible values so not possible.

Combining we have x > y from 1 and 2 says x > y only if x and y are positive. So Answer C.

However having solved that, I will concur that it is pretty trick problem and for most of the people picking number is better strategy.
User avatar
L
IanStewart
GMAT Tutor
Joined: 24 Jun 2008
Posts: 4128
Own Kudos [?]: 9247 [0]
Given Kudos: 91
 Q51  V47
Send PM
Re: are x , y > 0 ? 1) 2x-2y =1 2) x/y > 1 should we [#permalink] New post   19 Jul 2008, 23:36
Expert Reply
I would do the problem exactly as abhijit did above. To this question:

"should we always solve DS q's with taking sample numbers ?"

I would say no, not 'always'. I'd only try to solve DS questions with sample numbers if you cannot solve the problem conceptually or algebraically. It is often the case that if you don't pick a sufficient variety of sample numbers, you will reach an incorrect conclusion, and therefore a wrong answer.
User avatar
durgesh79
Manager
Manager
Joined: 27 May 2008
Posts: 231
Own Kudos [?]: 622 [0]
Given Kudos: 0
Send PM
Re: are x , y > 0 ? 1) 2x-2y =1 2) x/y > 1 should we [#permalink] New post   19 Jul 2008, 23:47
some people get it and some people dont but i feel that if you have two variablee inequality DS problem, plotting the conditions on xy plane is the best method.. only thing is, dont try this in exam without practise

question : x,y > 0 ... target area is Q1

statement 1 : line passes through Q1, Q2 and Q3 ... not suff
statement 2 : green area ... in Q1 and Q3 .. not suff

combine, line segament in blue, alwasy in Q1 ...suff ..answer
Attachment:
DSQ3.JPG
DSQ3.JPG [ 9.55 KiB | Viewed 1644 times ]
User avatar
abhaypratapsingh
Manager
Manager
Joined: 21 Mar 2006
Posts: 107
Own Kudos [?]: 104 [1]
Given Kudos: 0
Send PM
Re: are x , y > 0 ? 1) 2x-2y =1 2) x/y > 1 should we [#permalink] New post   20 Jul 2008, 00:10
1
Kudos
Let take one more example :
On number line , the distance between x and y is greater than distance between x and z. does z lie between x and y ?

1) xyz <0
2) xy<0

Now this resolves to is |X-Y| > |X-Z| ?

lets try solve algebracally and by sample data ... and see how much time each takes ...
User avatar
durgesh79
Manager
Manager
Joined: 27 May 2008
Posts: 231
Own Kudos [?]: 622 [0]
Given Kudos: 0
Send PM
Re: are x , y > 0 ? 1) 2x-2y =1 2) x/y > 1 should we [#permalink] New post   20 Jul 2008, 00:33
abhaypratapsingh wrote:
Let take one more example :
On number line , the distance between x and y is greater than distance between x and z. does z lie between x and y ?

1) xyz <0
2) xy<0

Now this resolves to is |X-Y| > |X-Z| ?

lets try solve algebracally and by sample data ... and see how much time each takes ...


is it E

statement 1 ... clearly not suff ... x,y,z all can be -ve and you never know z was on which side of x
statement 2 ... not suff ... doesn tell anything about Z

combine : ...z is Positive
and one of x or y is negative ....

if y is negative .... both x and z are positive and z can be on either side of x ... not suff
User avatar
mrblack
Manager
Manager
Joined: 27 Apr 2008
Posts: 137
Own Kudos [?]: 208 [0]
Given Kudos: 1
Send PM
Re: are x , y > 0 ? 1) 2x-2y =1 2) x/y > 1 should we [#permalink] New post   30 Jul 2008, 16:27
durgesh79 wrote:
some people get it and some people dont but i feel that if you have two variablee inequality DS problem, plotting the conditions on xy plane is the best method.. only thing is, dont try this in exam without practise

question : x,y > 0 ... target area is Q1

statement 1 : line passes through Q1, Q2 and Q3 ... not suff
statement 2 : green area ... in Q1 and Q3 .. not suff

combine, line segament in blue, alwasy in Q1 ...suff ..answer
Attachment:
DSQ3.JPG


Isn't the green area colored incorrectly? If x/y > 1, that means that x>y. The graph should than be colored such that everything to the right of the line y=x is green. Am I missing something?
User avatar
L
IanStewart
GMAT Tutor
Joined: 24 Jun 2008
Posts: 4128
Own Kudos [?]: 9247 [0]
Given Kudos: 91
 Q51  V47
Send PM
Re: are x , y > 0 ? 1) 2x-2y =1 2) x/y > 1 should we [#permalink] New post   30 Jul 2008, 18:46
Expert Reply
mrblack wrote:
Isn't the green area colored incorrectly? If x/y > 1, that means that x>y. The graph should than be colored such that everything to the right of the line y=x is green. Am I missing something?


If x/y > 1, that means that:

x > y if y > 0
x < y if y < 0

Remember, we need to reverse the inequality if we multiply both sides by a negative number, and y can certainly be negative.
User avatar
mrblack
Manager
Manager
Joined: 27 Apr 2008
Posts: 137
Own Kudos [?]: 208 [0]
Given Kudos: 1
Send PM
Re: are x , y > 0 ? 1) 2x-2y =1 2) x/y > 1 should we [#permalink] New post   30 Jul 2008, 18:52
IanStewart wrote:
mrblack wrote:
Isn't the green area colored incorrectly? If x/y > 1, that means that x>y. The graph should than be colored such that everything to the right of the line y=x is green. Am I missing something?


If x/y > 1, that means that:

x > y if y > 0
x < y if y < 0

Remember, we need to reverse the inequality if we multiply both sides by a negative number, and y can certainly be negative.


Thanks. That's a very good point. I got it now.



Archived Topic
Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Where to now? Join ongoing discussions on thousands of quality questions in our Data Sufficiency (DS) Forum
Still interested in this question? Check out the "Best Topics" block above for a better discussion on this exact question, as well as several more related questions.
Thank you for understanding, and happy exploring!
GMAT Club Bot
gmatclubot
Re: are x , y > 0 ? 1) 2x-2y =1 2) x/y > 1 should we [#permalink]
30 Jul 2008, 18:52
Moderators:
Bunuel
Math Expert
92933 posts
yashikaaggarwal
Senior Moderator - Masters Forum
3137 posts
GMATBusters
GMAT Tutor
1905 posts

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne
Main navigation
GMAT Resources
Partners
MBA Resources
www.gmac.com|www.mba.com | | GMAT Club Rules | Terms and Conditions