GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 20 Oct 2019, 05:06 GMAT Club Daily Prep

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

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.  If none of x, y, & z equals to 0, is x^4y^5z^6 > 0?

 new topic post reply Question banks Downloads My Bookmarks Reviews Important topics
Author Message
TAGS:

Hide Tags

Math Expert V
Joined: 02 Sep 2009
Posts: 58434
If none of x, y, & z equals to 0, is x^4y^5z^6 > 0?  [#permalink]

Show Tags 00:00

Difficulty:   15% (low)

Question Stats: 82% (00:52) correct 18% (01:32) wrong based on 66 sessions

HideShow timer Statistics

If none of x, y, & z equals to 0, is $$x^4y^5z^6 > 0$$?

(1) $$y > x^4$$

(2) $$y > z^5$$

_________________
SC Moderator P
Status: GMAT - Pulling Quant and Verbal together
Joined: 04 Sep 2017
Posts: 237
Location: United States (OH)
GPA: 3.6
WE: Sales (Computer Software)
Re: If none of x, y, & z equals to 0, is x^4y^5z^6 > 0?  [#permalink]

Show Tags

Bunuel wrote:
If none of x, y, & z equals to 0, is $$x^4y^5z^6 > 0$$?

(1) $$y > x^4$$

(2) $$y > z^5$$

Statement (1) tells us that y >0 because x^4 must be positive.

This is sufficient. If neither x, y, or z = 0 and y is positive, then we know that $$x^4y^5z^6 > 0$$ = positive

Statement (2) does not tell us that y is positive or negative. z could be negative which would make $$z^5$$ negative.

Not Sufficient.

_________________
Would I rather be feared or loved? Easy. Both. I want people to be afraid of how much they love me.

How to sort questions by Topic, Difficulty, and Source:
https://gmatclub.com/forum/search.php?view=search_tags
Senior Manager  G
Joined: 13 Feb 2018
Posts: 450
GMAT 1: 640 Q48 V28 Re: If none of x, y, & z equals to 0, is x^4y^5z^6 > 0?  [#permalink]

Show Tags

x and z will always be positive, despite the +- nature of x,z as they have even powers.
We have to detect weather y is + or -

1. y is greater than positive $$x^4$$. y is positive. suff.
2. as we dont know the +- nature of z, we cant say for sure y is positive or not. not suff

IMO
Ans: A
BSchool Forum Moderator G
Joined: 23 May 2018
Posts: 546
Location: Pakistan
If none of x, y, & z equals to 0, is x^4y^5z^6 > 0?  [#permalink]

Show Tags

Bunuel wrote:
If none of x, y, & z equals to 0, is $$x^4y^5z^6 > 0$$?

(1) $$y > x^4$$

(2) $$y > z^5$$

For $$x^4y^5z^6 > 0$$ to be true, $$x^4$$, $$y^5$$ and $$z^6$$ have to be all positive numbers.

x and z could be negative numbers themselves but their positive even powers will turn them into positive numbers.

The real question here is if y is a positive number or negative.

(1) $$y > x^4$$

$$x^4$$ we know is an even number because of the positive even power of x and if y is greater than that, it means y is a positive number.

Thus, Positive x Positive x Positive > 0

SUFFICIENT

(2) $$y > z^5$$

If z is positive, $$z^5$$ will be positive and a y greater than that will be positive too. That will result in Even x Even x Even > 0

However, if z is negative, $$z^5$$ will be negative as well and a y greater than that could either be negative or positive.

Thus, Positive x Negative x Positive < 0

INSUFFICIENT

The answer is A.
_________________
If you can dream it, you can do it.

Practice makes you perfect.

Kudos are appreciated.

Originally posted by MsInvBanker on 27 Sep 2018, 09:55.
Last edited by MsInvBanker on 29 Sep 2018, 07:40, edited 1 time in total.
VP  D
Joined: 31 Oct 2013
Posts: 1465
Concentration: Accounting, Finance
GPA: 3.68
WE: Analyst (Accounting)
Re: If none of x, y, & z equals to 0, is x^4y^5z^6 > 0?  [#permalink]

Show Tags

Bunuel wrote:
If none of x, y, & z equals to 0, is $$x^4y^5z^6 > 0$$?

(1) $$y > x^4$$

(2) $$y > z^5$$

$$x^4$$ and $$z^6$$yields a positive result . thus we all about need to know whether y is positive.

Statement 1: $$y>x^4$$. $$x^4$$ will always be positive. thus y has to be positive. Sufficient.

Statement : $$y>z^5$$. NOT clear. z= -2.$$z^5 = -32$$ and y = -2. NOT sufficient.

The best answer is A. Re: If none of x, y, & z equals to 0, is x^4y^5z^6 > 0?   [#permalink] 29 Sep 2018, 07:32
Display posts from previous: Sort by

If none of x, y, & z equals to 0, is x^4y^5z^6 > 0?

 new topic post reply Question banks Downloads My Bookmarks Reviews Important topics

 Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne  