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# DS: XY

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Manager
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07 Sep 2006, 10:10
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SVP
Joined: 05 Jul 2006
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07 Sep 2006, 10:22
B

FROM ONE

X^2/X(Y+1) < 1

X/(Y+1)<1 WE KNOW THAT Y+1 IS +VE

THERFORE

X<Y+1

WE CAN NEVER KNOW IF X<Y OR NOT

FROM TWO

XY/Y(Y-1) <1

X/(Y-1) < 1 AND SURE Y-1 IS +VE

THUS X<Y-1 THUS SURE X<Y

VP
Joined: 02 Jun 2006
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07 Sep 2006, 10:23
Same calculation..

S1 is insufficient.

From S2: x < y-1 => x < y Sufficient.

yezz wrote:
B

FROM ONE

X^2/X(Y+1) < 1

X/(Y+1)<1 WE KNOW THAT Y+1 IS +VE

THERFORE

X<Y+1

WE CAN NEVER KNOW IF X<Y OR NOT

FROM TWO

XY/Y(Y-1) <1

X/(Y-1) < 1 AND SURE Y-1 IS +VE

THUS X<Y-1 THUS SURE X<Y

CEO
Joined: 20 Nov 2005
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Schools: Completed at SAID BUSINESS SCHOOL, OXFORD - Class of 2008
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07 Sep 2006, 14:26
Either B or E. See the bold part below.

Question is
X-Y < 0 ???

St1: X^2/(XY+X) Since both X and Y are +ve both numerator and denominator are +ve and we can rewrite the equation as
X^2 < XY+X
X < Y+1
X-Y <1: INSUFF

St2: I am not sure if statement says XY/(Y^2-Y) OR (XY/Y^2)-Y

In case of XY/(Y^2-Y) <1
XY < Y^2 - Y
X < Y-1
X-Y < -1 : SUFF

In case of (XY/Y^2)-Y < 1
X/Y < Y
X < Y^2
X-Y^2 < 0 then X-Y could be +ve (For X = 5 and Y = 4) or -ve (for X = 5 and Y = 6): INSUFF
_________________

SAID BUSINESS SCHOOL, OXFORD - MBA CLASS OF 2008

Senior Manager
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07 Sep 2006, 15:58
i think its E

as 2) says (XY/Y^2)-Y < 1

i think there is no ambiguity because 1) specifically says

X^2/(XY+X) < 1

so the question writer knows to put the parantheses in the form a/(b). So we cannot assume 2 to be ambiguous.
Manager
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07 Sep 2006, 16:45
Statement 1:

x (x)
______ < 1

x (y + 1)

Therefore, x < y + 1

When x is 2, y could also be 2, 3, 4, 4.5 etc.
INSUFF

Statement 2 becomes,

xy < y^2 - y
then, xy + y < y^2
and finally, y(x+1) < y^2

x+1<y

In order for this statement to hold true, Y must always be greater than X. Right?

Ans. B
Intern
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08 Sep 2006, 06:05
I think it is E because 2) is written as XY/Y^2 - Y not XY/(Y^2-Y)
Director
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09 Sep 2006, 18:27
This is just a badly written question.....I'm pretty sure the questions on the GMAT should leave no ambiguity about what's in the denominator of an expression vs what's in another expression.

I went with B, but I see why the answer is E
09 Sep 2006, 18:27
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