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absolute values

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absolute values

by resilient » Fri Mar 14, 2008 10:10 pm
Is x times absolute value Y > y^2

1. x>y

2.y>0

qa is C


With abosulute value questions you must account for both negative situation and positive situation. So I did! But it came out wrong. Can someone please show me how i went wrong. I then picked values to test each situation.

-y^2 >x times absolute value Y > y^2
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Source: — Data Sufficiency |
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Re: absolute values

by gabriel » Sat Mar 15, 2008 3:38 am
Enginpasa1 wrote:Is x times absolute value Y > y^2

1. x>y

2.y>0

qa is C


With abosulute value questions you must account for both negative situation and positive situation. So I did! But it came out wrIng. Can someone please show me how i went wrong. I then picked values to test each situation.

-y^2 >x times absolute value Y > y^2
In any DS question it is very necessary that you understand the question stem properly and also that you infer the right meaning from it.

Take a close look at the above stem. It asks if x*mod(y)>y^2. Over here the point to be noted is that mod(y) and y^2 will always remain positive, so the only thing that matters is whether x is positive or negative and whether x is > y.

The statement will be true only if x>0 and mod(x)>mod(y) (Think about why it should be this way, why isn't it enough that x>y).

The first statement says x > y,

Let us consider two cases

Case 1 x=5 and y=-6 .. 5*mod(-6) = 30 and (-6)^2 =36 .. 30<36
Case2 x=7 and y = -6.. 7*6=42 and 6^2 =36.. 42>36 .. So we dont get a definite answer .. hence insufficient.

Statement 2 says y>0 .. this again is obviously insufficient as it says nothing about x..

Combine the 2 and we get x > y and y > 0 .. so this satisfies the condition that x>0 and mod(x) > mod(y) and hence combined they both are sufficient.

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Re: absolute values

by xeqtr » Sat Mar 15, 2008 12:16 pm
Hi!

since you have x|y|>y^2,

1. x>y; x=-1 y=-2 left hand you end up with - whereas right hand you'll always end up with +. so not sufficient unless you know x is positive as well

2. no info about x.

combined: x>y>0, now you know x is positive and greater than y, so you have:(some number x > y)|y| > y^2. Sufficient.
Enginpasa1 wrote:Is x times absolute value Y > y^2

1. x>y

2.y>0

qa is C


With abosulute value questions you must account for both negative situation and positive situation. So I did! But it came out wrong. Can someone please show me how i went wrong. I then picked values to test each situation.

-y^2 >x times absolute value Y > y^2
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moderator

by resilient » Sat Mar 15, 2008 12:48 pm
my weakness is not the math. As the moderator explained, I failed to understand the gist of the question. I often do this and need to fix it, especially since I know the math.
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