It is currently 23 Nov 2017, 10:02

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

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

If the function Q is defined by the formula Q = 5w/(4x(z^2))

Author Message
TAGS:

Hide Tags

Intern
Joined: 02 Mar 2012
Posts: 8

Kudos [?]: 17 [0], given: 0

If the function Q is defined by the formula Q = 5w/(4x(z^2)) [#permalink]

Show Tags

20 Apr 2012, 20:05
6
This post was
BOOKMARKED
00:00

Difficulty:

25% (medium)

Question Stats:

74% (01:26) correct 26% (01:40) wrong based on 413 sessions

HideShow timer Statistics

If the function Q is defined by the formula Q = 5w/(4x(z^2)), by what factor will Q be multiplied if w is quadrupled, x is doubled, and z is tripled?

A. 1/9
B. 2/9
C. 4/9
D. 3/9
E. 2/27
[Reveal] Spoiler: OA

Last edited by Bunuel on 21 Apr 2012, 00:11, edited 1 time in total.
Edited the question and added the OA

Kudos [?]: 17 [0], given: 0

Math Expert
Joined: 02 Sep 2009
Posts: 42338

Kudos [?]: 133122 [5], given: 12415

Show Tags

21 Apr 2012, 00:10
5
KUDOS
Expert's post
4
This post was
BOOKMARKED
gmattest27 wrote:
If the function Q is defined by the formula Q = 5w/4xz^2 , by what factor will Q be multi-plied if w is quadrupled, x is doubled, and z is tripled?

If the function Q is defined by the formula Q = 5w/(4x(z^2)), by what factor will Q be multiplied if w is quadrupled, x is doubled, and z is tripled?
A. 1/9
B. 2/9
C. 4/9
D. 3/9
E. 2/27

Given: $$Q=\frac{5w}{4x*z^2}$$.

Now, quadruple $$w$$, so make it $$4w$$; double $$x$$ so make it $$2x$$; triple $$z$$ and substitute these values instead of $$x$$, $$y$$, and $$z$$ in the original equation:

$$\frac{5(4w)}{4(2x)*(3z)^2}=\frac{4*5w}{4*2x*9*z^2}=\frac{4*5w}{18*(4x*z^2)}=\frac{4}{18}*\frac{5w}{4x*z^2}=\frac{2}{9}*\frac{5w}{4x*z^2}$$. Thus Q is multiplied by $$\frac{2}{9}$$.

Else plug-in values for $$x$$, $$y$$, and $$z$$. Let $$x=y=z=1$$ --> $$Q=\frac{5w}{4x*z^2}=\frac{5}{4}$$.

$$4w=4$$, $$2x=2$$ and $$3z=3$$ --> $$\frac{5*4}{4*2*3^2}=\frac{4}{18}*\frac{5}{4}=\frac{2}{9}*\frac{5}{4}$$. Thus Q is multiplied by $$\frac{2}{9}$$.

Hope it's clear.
_________________

Kudos [?]: 133122 [5], given: 12415

Math Expert
Joined: 02 Sep 2009
Posts: 42338

Kudos [?]: 133122 [0], given: 12415

Re: If the function Q is defined by the formula Q = 5w/(4x(z^2)) [#permalink]

Show Tags

21 Jun 2013, 03:48
Bumping for review and further discussion*. Get a kudos point for an alternative solution!

*New project from GMAT Club!!! Check HERE

All DS Functions and Custom Characters questions: search.php?search_id=tag&tag_id=40
All PS Functions and Custom Characters questions: search.php?search_id=tag&tag_id=61

_________________

Kudos [?]: 133122 [0], given: 12415

Intern
Joined: 22 May 2013
Posts: 48

Kudos [?]: 18 [1], given: 10

Concentration: General Management, Technology
GPA: 3.9
WE: Information Technology (Computer Software)
Re: If the function Q is defined by the formula Q = 5w/(4x(z^2)) [#permalink]

Show Tags

22 Jun 2013, 01:53
1
KUDOS
gmattest27 wrote:
If the function Q is defined by the formula Q = 5w/(4x(z^2)), by what factor will Q be multiplied if w is quadrupled, x is doubled, and z is tripled?

A. 1/9
B. 2/9
C. 4/9
D. 3/9
E. 2/27

We just need to find the factor thats all,

x-> doubled -> 2x
z-> tripled -> 3Z
Hence, Z^2 = 9Z^2

W is in numerator, and x*z in denominator.

Hence,
Additional factor being introduced = 4/2*9

=4/18 = 2/9 = B
_________________

Kudos [?]: 18 [1], given: 10

Non-Human User
Joined: 09 Sep 2013
Posts: 15511

Kudos [?]: 283 [0], given: 0

Re: If the function Q is defined by the formula Q = 5w/(4x(z^2)) [#permalink]

Show Tags

16 Jul 2014, 21:37
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.
_________________

Kudos [?]: 283 [0], given: 0

Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 7748

Kudos [?]: 17861 [0], given: 235

Location: Pune, India
Re: If the function Q is defined by the formula Q = 5w/(4x(z^2)) [#permalink]

Show Tags

16 Jul 2014, 23:06
gmattest27 wrote:
If the function Q is defined by the formula Q = 5w/(4x(z^2)), by what factor will Q be multiplied if w is quadrupled, x is doubled, and z is tripled?

A. 1/9
B. 2/9
C. 4/9
D. 3/9
E. 2/27

This is a very simple case of joint variation. Check out this link for a discussion on joint variation: http://www.veritasprep.com/blog/2013/02 ... g-jointly/
_________________

Karishma
Veritas Prep | GMAT Instructor
My Blog

Get started with Veritas Prep GMAT On Demand for \$199

Veritas Prep Reviews

Kudos [?]: 17861 [0], given: 235

SVP
Status: The Best Or Nothing
Joined: 27 Dec 2012
Posts: 1851

Kudos [?]: 2722 [0], given: 193

Location: India
Concentration: General Management, Technology
WE: Information Technology (Computer Software)
Re: If the function Q is defined by the formula Q = 5w/(4x(z^2)) [#permalink]

Show Tags

16 Jul 2014, 23:54
w becomes 4w ......... Resultant = 4

x becomes 2x ............ Resultant = 2

z becomes 3z ............. Resultant $$= 3^2 = 9$$ (As z is sitting under a square sign)

Multiplication factor = $$\frac{4}{2*9} = \frac{2}{9}$$

_________________

Kindly press "+1 Kudos" to appreciate

Kudos [?]: 2722 [0], given: 193

Non-Human User
Joined: 09 Sep 2013
Posts: 15511

Kudos [?]: 283 [0], given: 0

Re: If the function Q is defined by the formula Q = 5w/(4x(z^2)) [#permalink]

Show Tags

06 Jan 2017, 12:47
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.
_________________

Kudos [?]: 283 [0], given: 0

Senior Manager
Joined: 25 Mar 2013
Posts: 275

Kudos [?]: 35 [0], given: 101

Location: United States
Concentration: Entrepreneurship, Marketing
GPA: 3.5
Re: If the function Q is defined by the formula Q = 5w/(4x(z^2)) [#permalink]

Show Tags

09 Jan 2017, 15:53
Just understand words Quadrupled = 4 times
Q = $$\frac{5w}{4x z^{2}}$$
$$\frac{5 x 4w}{4(2x) . (3z)^{2}}$$
Take out Q factor
$$\frac{4}{18}$$
$$\frac{2}{9}$$
B
_________________

I welcome analysis on my posts and kudo +1 if helpful. It helps me to improve my craft.Thank you

Kudos [?]: 35 [0], given: 101

Director
Joined: 12 Nov 2016
Posts: 794

Kudos [?]: 37 [0], given: 165

Re: If the function Q is defined by the formula Q = 5w/(4x(z^2)) [#permalink]

Show Tags

20 Feb 2017, 19:09
I don't understand how Bunuel gets 18 in the denominator in the third step.

Kudos [?]: 37 [0], given: 165

Math Expert
Joined: 02 Sep 2009
Posts: 42338

Kudos [?]: 133122 [0], given: 12415

Re: If the function Q is defined by the formula Q = 5w/(4x(z^2)) [#permalink]

Show Tags

20 Feb 2017, 23:59
Nunuboy1994 wrote:
I don't understand how Bunuel gets 18 in the denominator in the third step.

4*2x*9*z^2 = 18*(4x*z^2).
_________________

Kudos [?]: 133122 [0], given: 12415

Re: If the function Q is defined by the formula Q = 5w/(4x(z^2))   [#permalink] 20 Feb 2017, 23:59
Display posts from previous: Sort by