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# Is (x^7)(y^2)(z^3) > 0 ? (1) yz < 0 (2) xz > 0

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Manager
Joined: 28 Jul 2013
Posts: 85
Location: India
Concentration: Marketing, Strategy
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29 Mar 2014, 06:35

Group the equation as follows:
(x^4)(x^3)(y^2)(z^3)

y^2 will always be +ive
x^4 will be positive
let x and z be positive (satisfying the second statement): so (x^3)(y^3) will be positive and hence the whole thing will be +ive

Now let x and z be -ve (again satisfying the second statement): so (x^3) will be negative and (z^3) will also be negative. The product will be positive.
Intern
Joined: 10 Mar 2014
Posts: 14
Location: United States
Concentration: General Management, Technology
GMAT 1: 740 Q50 V40
WE: Information Technology (Computer Software)

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09 Apr 2014, 13:37
Is X[7]Y[2]Z[3] > 0?
1. yz < 0
2. xz > 0

I am sure I am missing something. Can some one help?
I chose B with the below logic:
xz > 0
so XZ[3] > 0
So the question really becomes (XZ)[3] X[4] Y[2]
From 2, we know that XZ > 0 And X[4] and Y[2] cannot be negative. There by "B" is sufficient?
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Re: M25-34 GMAT Club Test [#permalink]

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09 Apr 2014, 23:18
Miraarun12345 wrote:
Is X[7]Y[2]Z[3] > 0?
1. yz < 0
2. xz > 0

I am sure I am missing something. Can some one help?
I chose B with the below logic:
xz > 0
so XZ[3] > 0
So the question really becomes (XZ)[3] X[4] Y[2]
From 2, we know that XZ > 0 And X[4] and Y[2] cannot be negative. There by "B" is sufficient?

Statement 2 is sufficient except in case y is 0. If y is 0, x^7*y^2*z^3 will be 0, not positive. If y is not 0, it will be positive. Hence statement 2 alone is not sufficient. Statement 1 tells you that y is not 0 (because yz is less than 0). Hence you need both statements.

(C)
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Get started with Veritas Prep GMAT On Demand for $199 Veritas Prep Reviews Intern Joined: 08 Apr 2014 Posts: 12 Re: M25-34 GMAT Club Test [#permalink] ### Show Tags 10 Apr 2014, 00:12 If there would have been a >= sign, xz>0 should have been sufficient but as it is not, we need the first statement to confirm that Y is not equal to zero. Intern Joined: 04 Mar 2011 Posts: 15 Re: Is (x^7)(y^2)(z^3) > 0 ? (1) yz < 0 (2) xz > 0 [#permalink] ### Show Tags 11 Apr 2014, 03:06 tricky question but loving it. thanks for this and for the explanations. I chose 'B' but Burnel nailed it by giving me insight into the reasoning... Current Student Joined: 02 Jul 2012 Posts: 211 Location: India Schools: IIMC (A) GMAT 1: 720 Q50 V38 GPA: 2.6 WE: Information Technology (Consulting) Re: Is (x^7)(y^2)(z^3) > 0 ? (1) yz < 0 (2) xz > 0 [#permalink] ### Show Tags 21 Oct 2014, 12:12 enigma123 wrote: Is $$(x^7)(y^2)(z^3)>0$$ (1) yz<0 (2) xz>0 Ha Ha Ha Ha.. Another question that caught me off guard. 1. This is insufficient. We don't know anything about the sign of x 2. This one seemed perfect, till I came to know of a possibility of y = 0. Combining 1 & 2 We would come to know that the prod. will be less than 0 and that none of the values will be 0. _________________ Give KUDOS if the post helps you... Intern Joined: 13 May 2015 Posts: 1 Re: Is (x^7)(y^2)(z^3) > 0 ? (1) yz < 0 (2) xz > 0 [#permalink] ### Show Tags 17 May 2015, 11:22 Guys, is there any difference between (y^2) and (y)^2. We can be sure that (y)^2 is positive but can we also be sure that (y^2) is positive? (forget about y=0 for a moment) thank you Veritas Prep GMAT Instructor Joined: 16 Oct 2010 Posts: 7942 Location: Pune, India Re: Is (x^7)(y^2)(z^3) > 0 ? (1) yz < 0 (2) xz > 0 [#permalink] ### Show Tags 17 May 2015, 19:35 1 This post received KUDOS Expert's post octenisept wrote: Guys, is there any difference between (y^2) and (y)^2. We can be sure that (y)^2 is positive but can we also be sure that (y^2) is positive? (forget about y=0 for a moment) thank you (y^2) and (y)^2 are the same. In both cases, y is squared. y could be anything - the whole of it is squared in both cases. If y = 2a + b, both representations give (2a + b)^2 = 4a^2 + b^2 + 4ab _________________ Karishma Veritas Prep | GMAT Instructor My Blog Get started with Veritas Prep GMAT On Demand for$199

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Re: Is (x^7)(y^2)(z^3) > 0 ? (1) yz < 0 (2) xz > 0 [#permalink]

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15 Jun 2016, 01:01
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Re: Is (x^7)(y^2)(z^3) > 0 ? (1) yz < 0 (2) xz > 0 [#permalink]

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06 Aug 2017, 07:35
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
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Re: Is (x^7)(y^2)(z^3) > 0 ? (1) yz < 0 (2) xz > 0   [#permalink] 06 Aug 2017, 07:35

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