Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized for You

we will pick new questions that match your level based on your Timer History

Track Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 500,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

The OA is C but I think it's E Statement (1) : clearly insufficient since we don't have the sign of Z (since it has an odd exponent) Statement (2) : clearly insufficient since Y can be 0 Both (1) and (2) : well yes Y can't be 0 but we still can't tell the sign of Z ! Consider this example : X=4 , Y= -1, Z= -1 ; we will have both statements right but the original expression will be negative

The OA is C but I think it's E Statement (1) : clearly insufficient since we don't have the sign of Z (since it has an odd exponent) Statement (2) : clearly insufficient since Y can be 0 Both (1) and (2) : well yes Y can't be 0 but we still can't tell the sign of Z ! Consider this example : X=4 , Y= -1, Z= -1 ; we will have both statements right but the original expression will be negative

Am I wrong ?

Inequality \(x^7*y^2*z^3>0\) to be true: I. \(x\) and \(z\) must be either both positive or both negative, AND II. \(y\) must not be zero.

(1) \(yz<0\) --> \(y\neq{0}\) (II is satisfied). Don't know about \(x\) and \(z\). Not sufficient.

(2) \(xz>0\) --> \(x\) and \(z\) are either both positive or both negative (I is satisfied). Don't know about \(y\). Not sufficient.

(1)+(2) Both conditions are satisfied. Sufficient.

Answer: C.

As for your doubt: we are not interested in the sign of \(z\), we need \(x\) and \(z\) to be be either both positive or both negative. Next, your example is not valid: x=4, y=-1, z=-1 --> yz=4>0 and xz=-4<0 and we are given that \(yz<0\) and \(xz>0\).

Am sorry, in the question is it x exponent z or the product between x and z ??

It is the product.

Is \((x^7)(y^2)(z^3) \gt 0\) ? reduced to is Is \((x)(y^2)(z) \gt 0\) ? -> I have removed the squared values as they do not play any role in changing the sign, but I kept \(y^2\) to consider the y=0 condition.
_________________

Inequality \(x^7*y^2*z^3>0\) to be true: I. \(x\) and \(z\) must be either both positive or both negative, AND II. \(y\) must not be zero.

(1) \(yz<0\) --> \(y\neq{0}\) (II is satisfied). Don't know about \(x\) and \(z\). Not sufficient.

(2) \(xz>0\) --> \(x\) and \(z\) are either both positive or both negative (I is satisfied). Don't know about \(y\). Not sufficient.

(1)+(2) Both conditions are satisfied. Sufficient.

Answer: C.

As for your doubt: we are not interested in the sign of \(z\), we need \(x\) and \(z\) to be be either both positive or both negative. Next, your example is not valid: x=4, y=-1, z=-1 --> yz=4>0 and xz=-4<0 and we are given that \(yz<0\) and \(xz>0\).

Hope it helps.

I have a doubt; Why can't B only be true because we care for x and z signs and from II either they both are +ive or -ive and this will provide us the result.
_________________

GGG (Gym / GMAT / Girl) -- Be Serious

Its your duty to post OA afterwards; some one must be waiting for that...

Inequality \(x^7*y^2*z^3>0\) to be true: I. \(x\) and \(z\) must be either both positive or both negative, AND II. \(y\) must not be zero.

(1) \(yz<0\) --> \(y\neq{0}\) (II is satisfied). Don't know about \(x\) and \(z\). Not sufficient.

(2) \(xz>0\) --> \(x\) and \(z\) are either both positive or both negative (I is satisfied). Don't know about \(y\). Not sufficient.

(1)+(2) Both conditions are satisfied. Sufficient.

Answer: C.

As for your doubt: we are not interested in the sign of \(z\), we need \(x\) and \(z\) to be be either both positive or both negative. Next, your example is not valid: x=4, y=-1, z=-1 --> yz=4>0 and xz=-4<0 and we are given that \(yz<0\) and \(xz>0\).

Hope it helps.

I have a doubt; Why can't B only be true because we care for x and z signs and from II either they both are +ive or -ive and this will provide us the result.

Please read the solution carefully.

Inequality \(x^7*y^2*z^3>0\) to be true: I. \(x\) and \(z\) must be either both positive or both negative, AND II. \(y\) must not be zero.

So for (2): we know that \(x\) and \(z\) are either both positive or both negative, BUT we don't know whether \(y\) equals to zero, because if it is then \(x^7*y^2*z^3=0\) and not more than zero.

Inequality \(x^7*y^2*z^3>0\) to be true: I. \(x\) and \(z\) must be either both positive or both negative, AND II. \(y\) must not be zero.

(1) \(yz<0\) --> \(y\neq{0}\) (II is satisfied). Don't know about \(x\) and \(z\). Not sufficient.

(2) \(xz>0\) --> \(x\) and \(z\) are either both positive or both negative (I is satisfied). Don't know about \(y\). Not sufficient.

(1)+(2) Both conditions are satisfied. Sufficient.

Answer: C.

As for your doubt: we are not interested in the sign of \(z\), we need \(x\) and \(z\) to be be either both positive or both negative. Next, your example is not valid: x=4, y=-1, z=-1 --> yz=4>0 and xz=-4<0 and we are given that \(yz<0\) and \(xz>0\).

Hope it helps.

I have a doubt; Why can't B only be true because we care for x and z signs and from II either they both are +ive or -ive and this will provide us the result.

Please read the solution carefully.

Inequality \(x^7*y^2*z^3>0\) to be true: I. \(x\) and \(z\) must be either both positive or both negative, AND II. \(y\) must not be zero.

So for (2): we know that \(x\) and \(z\) are either both positive or both negative, BUT we don't know whether \(y\) equals to zero, because if it is then \(x^7*y^2*z^3=0\) and not more than zero.

Hope it's clear.

Sorry to say but still I didn't get this...

Why are we checking Y must not be zero? Why can;t its be X or Z not to be zero
_________________

GGG (Gym / GMAT / Girl) -- Be Serious

Its your duty to post OA afterwards; some one must be waiting for that...

from statement 1: it depends on the value of x , x can be either positive or negative so statement 1 not sufficient

from statement 2: xz>0 case1: x +ve & z +ve case 2: x -ve & z-ve we know that y2 is +ve so from case 1:x7y2z3= (+)(+)(+)= + so from case 2:x7y2z3= (-)(+)(-)= + so B alone sufficient

from statement 1: it depends on the value of x , x can be either positive or negative so statement 1 not sufficient

from statement 2: xz>0 case1: x +ve & z +ve case 2: x -ve & z-ve we know that y2 is +ve so from case 1:x7y2z3= (+)(+)(+)= + so from case 2:x7y2z3= (-)(+)(-)= + so B alone sufficient

And again: please read the solution above.

The red part is the reason of many mistakes on GMAT.

Square of a number is not positive, it's non-negative --> \(y^2\geq{0}\). So for (2): we know that \(x\) and \(z\) are either both positive or both negative, BUT we don't know whether \(y\) equals to zero, because if it is, then \(x^7*y^2*z^3=0\) and not more than zero.

1) bc<0 2 options : +,- and -,+ but no info about a. Not sufficient

2) ac>0 2 options : +,+ and -,- but no info about b (That could equal 0 here's the trick in my opinion). Not sufficient

1+2) with 1 we know that \(b\neq{0}\) with 2 in both cases a^8*c*3 is > 0 \(+^7*+*3>0\) \(-^7*-^3>0\) as well We are not able to say so by just looking at statement 2 because \(b\) could be \(0\), using both statement we can discard that possibility. Sufficient C
_________________

It is beyond a doubt that all our knowledge that begins with experience.

1) bc<0 2 options : +,- and -,+ but no info about a. Not sufficient

2) ac>0 2 options : +,+ and -,- but no info about b (That could equal 0 here's the trick in my opinion)

1+2) with 1 we know that \(b\neq{0}\) with 2 in both cases a^8*c*3 is > 0 \(+^7*+*3>0\) \(-^7*-^3>0\) as well We are not able to say so by just looking at statement 2 because \(b\) could be \(0\), using both statement we can discard that possibility C

It’s quickly approaching two years since I last wrote anything on this blog. A lot has happened since then. When I last posted, I had just gotten back from...

Since my last post, I’ve got the interview decisions for the other two business schools I applied to: Denied by Wharton and Invited to Interview with Stanford. It all...

Marketing is one of those functions, that if done successfully, requires a little bit of everything. In other words, it is highly cross-functional and requires a lot of different...