absolute values

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resilient: Legendary Member; Posts: 789; Joined: Sun May 06, 2007 1:25 amFollowed by: 6 members; Location: Southern California, USA; Thanked: 15 times

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

Appetite for 700 and I scraped my plate!

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Source: Beat The GMAT — Data Sufficiency | Fri Mar 14, 2008 10:10 pm

gabriel: Legendary Member; Posts: 986; Joined: Wed Dec 20, 2006 11:07 amFollowed by: 1 member; Location: India; Thanked: 51 times

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.

Regards

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xeqtr: Senior | Next Rank: 100 Posts; Posts: 59; Joined: Sat Mar 15, 2008 8:44 am; Location: istanbul; Thanked: 2 times

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

Like this post

resilient: Legendary Member; Posts: 789; Joined: Sun May 06, 2007 1:25 amFollowed by: 6 members; Location: Southern California, USA; Thanked: 15 times

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.

Appetite for 700 and I scraped my plate!

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