Author 
Message 
Manager
Joined: 24 Sep 2008
Posts: 185
Schools: MIT / INSEAD / IIM  ABC

If x y, is (xy)/(x+y) > 1? 1.x>0 2.y<0 [#permalink]
Show Tags
06 Oct 2008, 18:10
Question Stats:
0% (00:00) correct 0% (00:00) wrong based on 0 sessions
HideShow timer Statistics
If x≠y, is (xy)/(x+y) > 1? 1.x>0 2.y<0 == Message from GMAT Club Team == This is not a quality discussion. It has been retired. If you would like to discuss this question please repost 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: 24 Sep 2008
Posts: 185
Schools: MIT / INSEAD / IIM  ABC

Re: DS  OG 11E Q139 [#permalink]
Show Tags
06 Oct 2008, 18:12
Last edited by GODSPEED on 09 Oct 2008, 03:14, edited 1 time in total.



SVP
Joined: 17 Jun 2008
Posts: 1504

Re: DS  OG 11E Q139 [#permalink]
Show Tags
07 Oct 2008, 00:10
GODSPEED wrote: In equality, this cannot be done unless we are absolutely sure that both denominator and nominator are positive. For example, 5/2 > 1 and hence we cannot say that 5 > 2. In order to know whether (xy)/(x+y) > 1, we need to know that both numerator and denominator are of the same sign and that numerator is greater than denominator. Stmt1 says that x is positive, but no clue about y. Hence, insufficient. Stmt2 says y is negative but again no clue about x. Hence, insufficient. Combining the two, (xy) is positive. But, again not sure whether (x+y) is positive or negative. Hence, E.



Senior Manager
Joined: 21 Apr 2008
Posts: 477
Schools: Kellogg, MIT, Michigan, Berkeley, Marshall, Mellon

Re: DS  OG 11E Q139 [#permalink]
Show Tags
07 Oct 2008, 02:04
My two cents: 1 Insuff. becasue if y=0, the sentence is not correct. 2 Insuff. (x+y)/(xy)>1? no if x<0 1+2 (x+y)/(xy)>1 always becasue x>0 Therefore, C OA? Cheers
_________________
mates, please visit my profile and leave comments http://gmatclub.com/forum/johnlewis1980sprofilefeedbackismorethanwelcome80538.html
I'm not linked to GMAT questions anymore, so, if you need something, please PM me
I'm already focused on my application package
My experience in my second attempt http://gmatclub.com/forum/p544312#p544312 My experience in my third attempt http://gmatclub.com/forum/630q47v28engineernonnativespeakermyexperience78215.html#p588275



Retired Moderator
Joined: 05 Jul 2006
Posts: 1741

Re: DS  OG 11E Q139 [#permalink]
Show Tags
07 Oct 2008, 03:48
GODSPEED wrote: If x≠y, is (xy)/(x+y) > 1?
1.x>0 2.y<0 rephrase question x^2  y^2 / x+y > 0 from 1 x is +ve however nothing is mentioned about / y/ value...insuff from 2 /x/ is not mentioned...insuff both E



Manager
Joined: 25 May 2008
Posts: 185

Re: DS  OG 11E Q139 [#permalink]
Show Tags
07 Oct 2008, 05:59
E. We must know if x>y.
1. x>0, so we have xy/x+y. If y>x and y<0, xy<0 and xy/x+y < 0. 2. y<0, so we have x(y)/x+(y), so x+y/xy, if x<y xy<0



VP
Joined: 30 Jun 2008
Posts: 1019

Re: DS  OG 11E Q139 [#permalink]
Show Tags
07 Oct 2008, 07:31
yezz wrote: GODSPEED wrote: If x≠y, is (xy)/(x+y) > 1?
1.x>0 2.y<0 rephrase question x^2  y^2 / x+y > 0 from 1 x is +ve however nothing is mentioned about / y/ value...insuff from 2 /x/ is not mentioned...insuff both E Yezz.. Can you explain how you rephrased the equation ??
_________________
"You have to find it. No one else can find it for you."  Bjorn Borg



Retired Moderator
Joined: 05 Jul 2006
Posts: 1741

Re: DS  OG 11E Q139 [#permalink]
Show Tags
07 Oct 2008, 16:18
amitdgr wrote: yezz wrote: GODSPEED wrote: If x≠y, is (xy)/(x+y) > 1?
1.x>0 2.y<0 Yezz.. Can you explain how you rephrased the equation ?? Apologies i did a mistake : (xy)/(x+y) > 1 = (xy)/(x+y)  1 = (xy)/(x+y)  (x+y)/(x+y) = (xy)  (x+y) / x+y = 2y/x+y question becomes is 2y/ x+y > 0 ( y +ve and x is ve, /x/>/y/) or ( y ve and x =ve , /x/>/y/) from 1 x>o no mentioning of y ......insuff from 2 y < 0 , no mentioning of x......insuff both x +ve , y ve however no info about /x/, and that of y..........E



Manager
Joined: 24 Sep 2008
Posts: 185
Schools: MIT / INSEAD / IIM  ABC

Re: DS  OG 11E Q139 [#permalink]
Show Tags
09 Oct 2008, 03:15
OA is E



VP
Joined: 17 Jun 2008
Posts: 1322

Re: DS  OG 11E Q139 [#permalink]
Show Tags
09 Oct 2008, 03:44
scthakur wrote: GODSPEED wrote: I picked up B  becuase i solved the equation, x cancels out and we are left with y 1 and hence we cannot say that 5 > 2.
In order to know whether (xy)/(x+y) > 1, we need to know that both numerator and denominator are of the same sign and that numerator is greater than denominator.
Stmt1 says that x is positive, but no clue about y. Hence, insufficient.
Stmt2 says y is negative but again no clue about x. Hence, insufficient.
Combining the two, (xy) is positive. But, again not sure whether (x+y) is positive or negative. Hence, E. One thing i dont understand is when we solve (xy)/(x+y)>1 then we get 2y>0 => y needs to be less than 0 and no dependency on x can u explain this thing .can we reduce the given equation or use the original one!!! == Message from GMAT Club Team == This is not a quality discussion. It has been retired. If you would like to discuss this question please repost 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.
_________________
cheers Its Now Or Never




Re: DS  OG 11E Q139
[#permalink]
09 Oct 2008, 03:44






