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If X+Y/Z > 0, is X<0 ? 1. X<Y 2. Z<0 [#permalink ]

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03 Feb 2008, 13:07
This topic is locked. If you want to discuss this question please re-post it in the respective forum.If X+Y/Z > 0, is X<0 ? 1. X<Y 2. Z<0

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Re: is X<0 ? [#permalink ]

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03 Feb 2008, 14:17
E x=1, y=2, z=-4

x=-2, y=-1, z=-0.1

satisfy both conditions. Insuff.

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Re: is X<0 ? [#permalink ]

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03 Feb 2008, 16:18

walker wrote:

E x=1, y=2, z=-4 x=-2, y=-1, z=-0.1 satisfy both conditions. Insuff.

here answer is C. together they are sufficient.

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Re: is X<0 ? [#permalink ]

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03 Feb 2008, 19:09

hmm . im getting E as well. i reduced stem to -x*z<y stat 1 doesnt tell us about z. insuff stat 2 doesnt tell us about x or y. insuff. together, i can have a negative x and positive y (since x<y) and a positive x and positive y. z is negative given from second statement. consider x=-2, z=-1 and y=-1 --> (-2)*(-1)<-1 --> 2<-1 ... not true consider x=2, z=-1 and y=4 --> (2)*(-1) <4 --> -2<4 ... true

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Re: is X<0 ? [#permalink ]

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03 Feb 2008, 21:03

answer is C 1 STATEMENT : X=4 Y=5 Z=5 X=-4 Y=15 Z=3 SO X CAN BE POSITIVE OR NEGATIVE 2 STATEMENT : X=2 Y=1 Z=-1 X=-2 Y=-10 Z=-1 SO X CAN BE POSITIVE OR NEGATIVE BOTH STATEMENTS TOGETHER X=-4 Y=-2 Z=-1/6 X HAS TO BE NEGATIVE IN ORDER TO FULFILL ALL CONDITIONS

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Re: is X<0 ? [#permalink ]

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03 Feb 2008, 22:33

neeraj.kaushal wrote:

answer is C 1 STATEMENT : X=4 Y=5 Z=5 X=-4 Y=15 Z=3 SO X CAN BE POSITIVE OR NEGATIVE 2 STATEMENT : X=2 Y=1 Z=-1 X=-2 Y=-10 Z=-1 SO X CAN BE POSITIVE OR NEGATIVE BOTH STATEMENTS TOGETHER X=-4 Y=-2 Z=-1/6 X HAS TO BE NEGATIVE IN ORDER TO FULFILL ALL CONDITIONS

I can not see why X must be negative! x can be positive: x =3, y = 4, z =-2

1. 3 + 4/(-2) =1 >0 satify

2. 3< 4

3. -2 < 0

All the conditions satified, why x must be negative?

E
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Re: is X<0 ? [#permalink ]

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04 Feb 2008, 14:30

Just a quick question, can I do X+Y/Z > 0 X > -(Y/Z) X < Y/Z Given Z -ve Y/Z is -Ve and Hence X is -ve. So, B only. Not sure if this is correct. -Jack

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Re: is X<0 ? [#permalink ]

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04 Feb 2008, 14:31

blog wrote:

If X+Y/Z > 0, is X<0 ? 1. X<Y 2. Z<0

1: insufficient (-1,1,0.5), (0.5,1,0.5)

2: insufficient (-1,-2,-1), (1,-2,-1)

1&2: insufficient:

(-4,-3,-0.25) and (3,4,-2) -> E

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Re: is X<0 ? [#permalink ]

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04 Feb 2008, 16:37

Has to be E.

As per St1: X can be both -ve and +ve to meet the result.

X Y Z

-4 -3 -0.5 > 0

2 4 2 > 0

Not suff.

As per St2 again: X can be both -ve and +ve to meet the result.

X Y Z

-3 -4 -1 > 0

3 -2 -1 > 0

3 2 -1 > 0

Not suff.

Combining 1 & 2:

X Y Z

-4 -3 -1 > 0...YES

3 4 -1 < 0...NO

3 4 -4 > 0...YES

X can be both -ve and +ve..

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Last edited by

suntaurian on 04 Feb 2008, 16:49, edited 1 time in total.

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Re: is X<0 ? [#permalink ]

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04 Feb 2008, 16:39

jackychamp wrote:

Just a quick question, can I do X+Y/Z > 0 X > -(Y/Z) X < Y/Z Given Z -ve Y/Z is -Ve and Hence X is -ve. So, B only. Not sure if this is correct. -Jack

Jack, How do you know that given Z is -ve, Y/Z can not be positive ? Y can be both positive or negative...hence so can X.

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Re: is X<0 ? [#permalink ]

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05 Feb 2008, 00:35

blog wrote:

walker wrote:

E x=1, y=2, z=-4 x=-2, y=-1, z=-0.1 satisfy both conditions. Insuff.

here answer is C. together they are sufficient.

blog, based on your feedback, I think the question is supposed to be:

If (X+Y)/Z > 0, is X<0 ?

1. X<Y

2. Z<0

Then the answer would be (C). Otherwise its (E)

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Re: is X<0 ? [#permalink ]

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05 Feb 2008, 11:38

incognito1 wrote:

blog wrote:

walker wrote:

E x=1, y=2, z=-4 x=-2, y=-1, z=-0.1 satisfy both conditions. Insuff.

here answer is C. together they are sufficient.

blog, based on your feedback, I think the question is supposed to be:

If (X+Y)/Z > 0, is X<0 ?

1. X<Y

2. Z<0

Then the answer would be (C). Otherwise its (E)

yeah Z is below both (X+Y) ?

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Re: is X<0 ? [#permalink ]

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05 Feb 2008, 12:24

blog wrote:

yeah Z is below both (X+Y) ?

The equation (X+Y)/Z > 0 is different from X+Y/Z > 0

The latter would be evaluated as:

X+(Y/Z) > 0

since when parenthesis are not specified, division is performed prior to addition.

for instance:

2 + 4/2 = 2 + (4/2) = 2 + 2 = 4

whereas

(2+4)/2 = 6/2 = 3

But I think you already knew this!

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