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macca
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vipin7um
|x-y| > |x| - |y|

Lets take condition 1.
1, y<x

again note that |x-y| >= |x| - |y|. The equality condition holds when x=y. By suggesting y<x, we ensure that the |x-y| != |x| - |y|.

2, xy < 0
if xy < 0, then they have to have opposite sign. Hence x != y.
=> |x-y| != |x| - |y|

HTH...


hmm...didn't quite get this....so what's your answer??
what did you mean with "again note that |x-y| >= |x| - |y|." when the
question stem says |x-y| > |x| - |y|
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E.

One can also pick numbers for x and y, and feed into the satatements,

Stat1 insufficient
Stat2 does not give much info

combined together, not sufficient
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gmatacer
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For these type of questions, I plugin value of x and y

x +ve and Y -ve, say x=3 and y = -2 (this satisfies above equation) and x>y
Now, x -ve and Y -ve, say x=-2 and y=-1(satisfies above equation) and x<y.
So, we can't say from option 1

Drills down to BCE

for same set values(above) for 1t set, x=3 and y=-2. xy(-6)<0 and for second set x=-2 and y=-1, xy(3)>0
Sp, we can't say from option 2 that xy is always less than 0

so, answer is E
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macca
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Anybody else :)
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B

1) If x and y both are positive/negative LHS = RHS.
If y is negative and x is positive, LHS > RHS
Not sufficient

2) xy < 0 means either x or y is negative.
If x is -ve & y positive; LHS > RHS
if y is -ve and x positive; Still LHS > RHS
Sufficent
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|x-y| > |X|-|Y|

|X-Y| is always positive no matter what X and Y are.

+ve > |X|-|Y| is the question.


A.

Since Y<X.
X -ve, Y-ve (say -2, -4) can be answered as Yes.
X +ve, Y -ve (say 4, -2) can be answered as yes.
X +ve, y +ve (say 6, 5) cannot be answered because LHS = RHS.
not sufficient.

B
XY <0
here X +ve, Y-ve (2, -4) can be answered as Yes.
X -ve, Y +ve (-4, 2) can also be answered as Yes.
X +ve and Y +ve cannot be less than Zero. same with X -ve and Y-ve.
Sufficient.

Answer is B.
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I picked E. I plugged in numbers and it didnt pan out either way.
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I'm going with C. OA please... :)
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macca
vipin7um
|x-y| > |x| - |y|

Lets take condition 1.
1, y<x

again note that |x-y| >= |x| - |y|. The equality condition holds when x=y. By suggesting y<x, we ensure that the |x-y| != |x| - |y|.

2, xy < 0
if xy < 0, then they have to have opposite sign. Hence x != y.
=> |x-y| != |x| - |y|

HTH...

hmm...didn't quite get this....so what's your answer??
what did you mean with "again note that |x-y| >= |x| - |y|." when the
question stem says |x-y| > |x| - |y|


My answer is D. Since using either condition we can remove the equality part of the inequality.

- Vipin
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Professor
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Quote:
Is |x-y| > |x| - |y| ?

1, y<x
2, xy < 0


using trail and error approach:

from i, if x = -1 and y = -3
|x-y| = |-1+3| = 2, and |x| - |y| = -2 so true..

if x = 3 and y = 1
|x-y| = |3-1| = 2, and |3| - |1| = 2 so not true.


from ii, x = -1 and y = 3
|x-y| = |-1-3| = 4, and |x| - |y| = -2 so true..

if x = 3 and y = -1
|x-y| = |3+1| = 4, and |x| - |y| = |3| - |-1| = 2 so true.

B is sufficient.....
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macca
Is |x-y| > |x| - |y| ?

1, y<x
2, xy < 0

How do I approach this kind of problem? :roll:

Any easy approch, within 2 min??

You convert this into simple form and try to get the values > 0 or < 0
z = |X-Y| -|X| +|Y|

St 1. Not suff. becaause we don't know range of X and Y
St2. Not suff. becayse we don't know

From St 1 and two
case 1
X>Y and X> 0 and Y <0

Z >0

case 2 X > Y and X< 0 and Y >0

Z < 0

Hence E


I revisited the problem I think its B.
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willget800
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B...

A is not suff, try {x,y} ==> {2,1} and {2,-3}
B is suff, try {x,y} ==> {-1,1} and {1,-1}
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Think about Number line....

A is not sufficient as |X-Y| is always positive but |X|-|Y| can be negative also depending on who is far away from origin.

and y<x will not tell us which point has higher absolute value, (x,y) can be (10, -20) and (10, -2) in first canse |X|-|Y| is negative and in second case its positive.

B is sufficient as it says x and y are of different sign that means |x-y|, will show distance between this two points.

While |x|-|Y| will show delta between individual distance which has to be smaller than |x-y|



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