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Re: DS  x and y positive [#permalink]
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04 Jul 2006, 11:10
gidimba wrote: Are x and y both positive?
1. 2x2y=1 2. x/y >1
please explain your answers 
(1) xy = 1/2, can't say if both are +ve (for e.g. 2,1.5 or 1.5, 2) (INSUFF)
(2) x/y > 1 ; {10, 5} or {10,5}. even combining both does not provide a definite answer.
(E)



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Joined: 11 May 2006
Posts: 258

shahnandan wrote: stmt 1,
x=o y= 1/2 NO x=3 y=2 1/2 YES
insuff
stmt2
x>y both can be negative or positive  insuff
together,
consider values for stmt1 as aboveE.
x=0 and y = 1/2 do not satisfy x/y > 1



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Joined: 11 May 2006
Posts: 258

Re: DS  x and y positive [#permalink]
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04 Jul 2006, 11:33
necromonger wrote: gidimba wrote: Are x and y both positive?
1. 2x2y=1 2. x/y >1
please explain your answers  (1) xy = 1/2, can't say if both are +ve (for e.g. 2,1.5 or 1.5, 2) (INSUFF) (2) x/y > 1 ; {10, 5} or {10,5}. even combining both does not provide a definite answer. (E)
(1) says x > y
(2) says x and y are either both +ve or both ve.
considering both together,
if x > y, then both need to be +ve to satisfy x/y > 1



Senior Manager
Joined: 20 Feb 2006
Posts: 331

haas_mba07 wrote: gidimba, Can we have the OA please?
1. x = y+1 , not suff
2. x/y>1 , not suff
using both.
(y+1)/y >1
1+(1/y) >1.
This means Y is +Ve. But X = y+1. so both x and y are +ve .. ==> C



Senior Manager
Joined: 20 Feb 2006
Posts: 331

shahnandan wrote: stmt 1,
x=o y= 1/2 NO x=3 y=2 1/2 YES
insuff
stmt2
x>y both can be negative or positive  insuff
together,
consider values for stmt1 as aboveE.
x/y >1 doesn't mean X >Y.. For ex 5/3 >1, but 5 isn't greater than 3.



CEO
Joined: 20 Nov 2005
Posts: 2894
Schools: Completed at SAID BUSINESS SCHOOL, OXFORD  Class of 2008

C
St1: This gives us x >y : INSUFF
St2: This gives us: Either both are +ve or both are ve. If both +ve then x>y, but if both ve then x < y. : INSUFF
Combined: Simply we get x > y and both are +ve : SUFF
_________________
SAID BUSINESS SCHOOL, OXFORD  MBA CLASS OF 2008



Senior Manager
Joined: 08 Jun 2004
Posts: 495
Location: Europe

Guys let me give you the OA.
OA is 'C'.
This is GMATPrep question.



Manager
Joined: 01 Jun 2006
Posts: 139

The answer clearly is C
(1) said that x>y
(2) said that x/y>1 so x,y must be both positive(x>y) or negative (x<y)
(1),(2) together we have x,y are both positive numbers.



Intern
Joined: 11 May 2004
Posts: 46
Location: USA

THE OA is C i think i saw this in powerprep
All u do is
X=2 Y=1.5
or X=1 Y= 1.5
B states X>Y, hence u can solve and only 1 solution X AND Y are POSTIIVE THUS C



GMAT Instructor
Joined: 04 Jul 2006
Posts: 1262
Location: Madrid

Are x and y both positive?
1. 2x2y=1
2. x/y >1
From (1) xy=1/2>0 (not sufficient (x,y) could be (3/2,1) or (2,3/2) or (0,1/2)... N. Suff
From (2), x and y are the same sign and x is further from 0 than is y.
(x,y) could be (3,1), (3,1)... N Suff
But together, x and y must be either both positive or both negative (from (2))
If x,y are both negative, x<y<0, so xy<0, so 2(xy) cannot be 1, which contradicts (1)
Therefore x any must both be positive Ans. C



Current Student
Joined: 28 Dec 2004
Posts: 3357
Location: New York City
Schools: Wharton'11 HBS'12

OK lets see...
question stem is x AND y BOTH +
1) 2x2y=1
2(xy)=1; which can be written as x=1/2 + y
insuff... x can be 1 and y=1.5 or x=1.5 and y=1
2) x/y > 1
well...DONT do anything like cross multiplication cause we dont know the signs of x or y. All we know is that X and Y have to have the same sign + or ve. Insuff
lets take em together
sub vaule for x
1/2y + 1 > 1; well this can only be true if Y is +ve...if Y is +ve then X is +ve (given in statement 2)..
C it is....
Hope this helps..its a very simple way of lookin at this problem..and time efficient too, since i dont have to plug in numbers...







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