XYZ>0, IS X>0?

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ebehboud: Senior | Next Rank: 100 Posts; Posts: 31; Joined: Sat Aug 23, 2008 8:23 pm; Location: Toronto; Thanked: 1 times; GMAT Score:610

by ebehboud » Sat May 02, 2009 11:40 am

XYZ> 0, is X>0?

1) XY>0
2) XZ>0

My reasoning is:
1) Either x,y >0, OR x,y<0 , and no information on Z. insufficient
2) either x,z>0, OR x,z<0, no information on Y. In sufficient.

Together: If X,Y, Z have to be >0 such that XYZ>0 therefor (C)

I don't have the OA.

Thanks ya'll

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Source: Beat The GMAT — Data Sufficiency | Sat May 02, 2009 11:40 am

mixpanda: Junior | Next Rank: 30 Posts; Posts: 28; Joined: Wed Apr 15, 2009 11:35 pm; Thanked: 1 times

by mixpanda » Sat May 02, 2009 1:43 pm

IMO the answer is C.

Neither statement is sufficient alone, but together you see that all three variables must be either negative or positive. Based on the initial assumption that XYZ is greater than zero, negative is ruled out. All variables are positive, so X is greater than 0.

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ebehboud: Senior | Next Rank: 100 Posts; Posts: 31; Joined: Sat Aug 23, 2008 8:23 pm; Location: Toronto; Thanked: 1 times; GMAT Score:610

by ebehboud » Sat May 02, 2009 4:41 pm

Thank you.

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danimmm: Junior | Next Rank: 30 Posts; Posts: 13; Joined: Sat Feb 21, 2009 10:02 pm; GMAT Score:580

by danimmm » Sun May 03, 2009 11:02 am

xz>0
so...
{X>0 and Z>0} or {X<0 and Z<0}

xy>0
so...
{X>0 and Y>0} or {X<0 and Y<0}

any way x,y and z must all have the same sign.
XYZ>0 => all positive.

X positive and u needed both ...
Answer- C

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chetanojha: Master | Next Rank: 500 Posts; Posts: 125; Joined: Sun Sep 16, 2007 1:38 pm; Thanked: 6 times

Re: XYZ>0, IS X>0?

by chetanojha » Sun May 03, 2009 11:12 am

Statement1: this stmt show X & Y both have same sign. No information about Z. Insufficient.

Statement 2: proves X&Z both have same sign. No information on Y. INSUFF.

Together, it prove X,Y and Z are all save sign and since XYZ>0 all are +ve. Hence X>0.

ebehboud wrote:XYZ> 0, is X>0?

1) XY>0
2) XZ>0

My reasoning is:
1) Either x,y >0, OR x,y<0 , and no information on Z. insufficient
2) either x,z>0, OR x,z<0, no information on Y. In sufficient.

Together: If X,Y, Z have to be >0 such that XYZ>0 therefor (C)

I don't have the OA.

Thanks ya'll

Like this post

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