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If xyz > 0, is x > 0? (1) xy > 0 (2) xz > 0

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SVP
SVP
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Joined: 21 Jul 2006
Posts: 1551
Followers: 8

Kudos [?]: 235 [0], given: 1

If xyz > 0, is x > 0? (1) xy > 0 (2) xz > 0 [#permalink] New post 31 Mar 2008, 11:43
00:00
A
B
C
D
E

Difficulty:

(N/A)

Question Stats:

100% (01:08) correct 0% (00:00) wrong based on 0 sessions
If xyz > 0, is x > 0?

(1) xy > 0

(2) xz > 0



Please explain your answer ;)
Current Student
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Joined: 28 Dec 2004
Posts: 3403
Location: New York City
Schools: Wharton'11 HBS'12
Followers: 13

Kudos [?]: 164 [0], given: 2

Re: DS: Is X positive? [#permalink] New post 31 Mar 2008, 11:48
has to be C..cause now if xz and xy are all positive than all of em are positive..
Senior Manager
Senior Manager
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Joined: 01 Feb 2005
Posts: 274
Followers: 1

Kudos [?]: 30 [0], given: 1

Re: DS: Is X positive? [#permalink] New post 31 Mar 2008, 18:01
i got E.... what if from A we have x = -1, y = -2. the product is >0 and from
B i get x = -1 and z = -3. the product is >0 but x in both the cases are -ve

same scenario but x = +ve and y = +ve from A and x = +ve and z = +ve. therefore from both the scenarios x could be again +ve or -ve. hence E is the best answer
Current Student
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Joined: 28 Dec 2004
Posts: 3403
Location: New York City
Schools: Wharton'11 HBS'12
Followers: 13

Kudos [?]: 164 [0], given: 2

Re: DS: Is X positive? [#permalink] New post 31 Mar 2008, 18:31
then how do you explain xyz>0..
Director
Director
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Joined: 01 May 2007
Posts: 795
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Kudos [?]: 79 [0], given: 0

Re: DS: Is X positive? [#permalink] New post 01 Apr 2008, 10:55
Agree with C, but is there a way to somehow solve it via computation...i got to here but couldn't get any further...


xy > 0
xz > 0
xyz > 0

x(y + z + yz) > 0

thoughts?
SVP
SVP
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Joined: 21 Jul 2006
Posts: 1551
Followers: 8

Kudos [?]: 235 [0], given: 1

Re: DS: Is X positive? [#permalink] New post 01 Apr 2008, 11:07
OA is C. Yes, X could be either positive or negative, but don't forget what it says in the question stem that xyz > 0, this statement wouldn't be true if X is negative, right? so all of them are positive. E would be correct if we weren't told that xyz > 0. Remember that xyz > 0 MUST HOLD
Re: DS: Is X positive?   [#permalink] 01 Apr 2008, 11:07
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If xyz > 0, is x > 0? (1) xy > 0 (2) xz > 0

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