ABSOLUTE VALUE YES/NO DS

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cramya: Legendary Member; Posts: 2467; Joined: Thu Aug 28, 2008 6:14 pmFollowed by: 11 members; Thanked: 331 times

by cramya » Tue Dec 09, 2008 8:33 pm

Is |X-1| < 1 ?

1) (x-1)^2 <= 1

2) x^2 - 1 > 0

Source: 2008 GMAT Club

OA:E

I think its [spoiler]B)[/spoiler](The reason being if its equal to or greater we can answer the question with a definite NO which makes it SUFFICIENT)

Comments/feedback welcome!

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Source: Beat The GMAT — Data Sufficiency | Tue Dec 09, 2008 8:33 pm

Stuart@KaplanGMAT: GMAT Instructor; Posts: 3225; Joined: Tue Jan 08, 2008 2:40 pmFollowed by: 614 members; Location: Toronto; Thanked: 1710 times; GMAT Score:800

Re: ABSOLUTE VALUE YES/NO DS

by Stuart@KaplanGMAT » Tue Dec 09, 2008 10:43 pm

cramya wrote:Is |X-1| < 1 ?

1) (x-1)^2 <= 1

2) x^2 - 1 > 0

Source: 2008 GMAT Club

OA:E

I think its [spoiler]B)[/spoiler](The reason being if its equal to or greater we can answer the question with a definite NO which makes it SUFFICIENT)

Comments/feedback welcome!

Is |X-1| < 1 ?

When will this be true?

Well, if x is between 0 and 2, we'll get a yes.

Every other value will give us a no.

(1) (x-1)^2 <= 1

x = 1.5 fits this rule and gives us a "yes" answer.
x = 2 fits this rule and gives us a "no" answer.
Insufficient!

(2) x^2 - 1 > 0

x = 1.5 fits this rule and gives us a "yes" answer.
x = 2 fits this rule and gives us a "no" answer.
Insufficient.

Together:

we can still choose both 1.5 and 2, so we can still get both a "yes" and a "no"... choose (E), not enough information.

Remember, we don't have to pick integers!

Stuart Kovinsky | Kaplan GMAT Faculty | Toronto

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cramya: Legendary Member; Posts: 2467; Joined: Thu Aug 28, 2008 6:14 pmFollowed by: 11 members; Thanked: 331 times

by cramya » Tue Dec 09, 2008 10:57 pm

Thanks so much again!

Remember, we don't have to pick integers!

This is hurting me from time and again! I am thinking this post hopefully reinstills the consideration of non integers in a DS when no info on x is given

Stmt II

I simplified

x^2>1
|x|>1

x>1 x<-1

Considered just integers which led me to B).

So going back to my question if x was given to be an integer would B) be the right choice?

Thanks Stuart!!!!!!

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Tryingmybest: Master | Next Rank: 500 Posts; Posts: 168; Joined: Thu Nov 13, 2008 4:34 am; Location: Pittsburgh; Thanked: 9 times

by Tryingmybest » Wed Dec 10, 2008 12:56 pm

Cramya ,Please see if this works

From 1 x^2 -2x+1 <= 1
x^2 -2x<=0
x^2<= 2x-- A

Not sufficient

From 2 x^2>1 => -x^2 < -1---B
Not sufficient

Add A and B => 0<=2x-1
2x>=1
x>=1/2

X=1/2 will satisfy the question, X=3 won't ..

So E

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albema: Newbie | Next Rank: 10 Posts; Posts: 6; Joined: Thu Dec 04, 2008 12:36 pm; GMAT Score:480

Re: ABSOLUTE VALUE YES/NO DS

by albema » Wed Dec 10, 2008 3:01 pm

cramya wrote:Is |X-1| < 1 ?

1) (x-1)^2 <= 1

2) x^2 - 1 > 0

Source: 2008 GMAT Club

OA:E

But 1) tells us that 0<X<2 so A is sufficient

Please explain am I right?

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