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Re: DS - x and y positive [#permalink]
 04 Jul 2006, 11:10
gidimba wrote: Are x and y both positive?
1. 2x-2y=1
2. x/y >1
please explain your answers -
(1) x-y = 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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Senior Manager
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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 above--E.
x=0 and y = -1/2 do not satisfy x/y > 1
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Re: DS - x and y positive [#permalink]
04 Jul 2006, 11:33
necromonger wrote: gidimba wrote: Are x and y both positive?
1. 2x-2y=1
2. x/y >1
please explain your answers - (1) x-y = 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
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Senior Manager
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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
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Senior Manager
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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 above--E.
x/y >1 doesn't mean X >Y.. For ex -5/-3 >1, but -5 isn't greater than -3.
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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
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Director
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Guys let me give you the OA. 
OA is 'C'.
This is GMATPrep question.
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Manager
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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.
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Manager
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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
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GMAT Instructor
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Are x and y both positive?
1. 2x-2y=1
2. x/y >1
From (1) x-y=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 x-y<0, so 2(x-y) cannot be 1, which contradicts (1)
Therefore x any must both be positive Ans. C
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OK lets see...
question stem is x AND y BOTH +
1) 2x-2y=1
2(x-y)=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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close
