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

 It is currently 22 Mar 2019, 15:43 ### 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. ### Request Expert Reply # If the function Q is defined by the formula Q = 5w/(4x(z^2))

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

### Hide Tags

Intern  Joined: 24 Feb 2011
Posts: 28
If the function Q is defined by the formula Q = 5w/(4x(z^2))  [#permalink]

### Show Tags

3 00:00

Difficulty:   25% (medium)

Question Stats: 72% (01:42) correct 28% (02:29) wrong based on 238 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

Originally posted by olivite on 04 Jun 2011, 12:33.
Last edited by Bunuel on 11 Dec 2012, 02:00, edited 3 times in total.
Edited the question and added the answer choices with OA
Retired Moderator B
Joined: 16 Nov 2010
Posts: 1402
Location: United States (IN)
Concentration: Strategy, Technology
Re: Direct and inverse proportionality  [#permalink]

### Show Tags

1
IN the expression Q=5w/4xz^2, substitute the values as mentioned :

So new expression is -> 5 * (4w)/(4 * (2x) * (3z)^2)

= 5 * w/(2x * 9 * z^2)

= (2/9) * 5w/4xz^2

= 2/9 * Q

So Q will be multiplied by the factor 2/9.
_________________

Formula of Life -> Achievement/Potential = k * Happiness (where k is a constant)

GMAT Club Premium Membership - big benefits and savings

Intern  Status: Don't worry about finding inspiration. It eventually come >>>>>>>
Joined: 31 May 2011
Posts: 23
Location: Î Ñ D Ï Â
Re: Direct and inverse proportionality  [#permalink]

### Show Tags

According to expression Q= 5w/4xz²
now, w'=4w,
x'=2x
z'=3z
Put these values in a same order, we get
Q'= 5(4w)/4(2x)(3z)²
Q'=5w/18xz²
Q'=2/9*(5w/4xz²)
So, Q'= 2/9(Q),q will be a multiple of factor 2/9.
This is the most effective way to solve such question. Director  Joined: 01 Feb 2011
Posts: 653
Re: Direct and inverse proportionality  [#permalink]

### Show Tags

$$Q = 5W/(4XZ^2)$$

Q1 = $$5(2W)/(4(2X)9X^2)$$ = 2/9 Q

So the factor is 2/9.
Intern  Joined: 02 Jan 2011
Posts: 9
Re: Direct and inverse proportionality  [#permalink]

### Show Tags

Hi guys,

I am sorry, but i still did not get this part.

Q'=5w/18xz²
to
Q'=2/9*(5w/4xz²)

Would anyone be able please to elaborate on it? I would really appreciate it.

Serge.
Math Expert V
Joined: 02 Sep 2009
Posts: 53792
Re: Direct and inverse proportionality  [#permalink]

### Show Tags

2
1
SergeNew wrote:
Hi guys,

I am sorry, but i still did not get this part.

Q'=5w/18xz²
to
Q'=2/9*(5w/4xz²)

Would anyone be able please to elaborate on it? I would really appreciate it.

Serge.

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.
_________________
Senior Manager  Joined: 13 Aug 2012
Posts: 419
Concentration: Marketing, Finance
GPA: 3.23
Re: If the function Q is defined by the formula Q = 5w/(4x(z^2))  [#permalink]

### Show Tags

1
$$Q=\frac{{5w}}{{4xz^2}}$$

$$Qmod=\frac{{5(4w)}}{{4(2x)(3z)^2}}$$
$$Qmod=\frac{{20w)}}{{72xz^2}}$$
$$Qmod=\frac{4}{18}*\frac{{5w}}{{4xz^2}}$$
$$Qmod=\frac{4}{18}*Q$$
$$Qmod=\frac{2}{9}*Q$$

_________________

Impossible is nothing to God.

Manager  Joined: 24 Mar 2010
Posts: 64
Re: If the function Q is defined by the formula Q = 5w/(4x(z^2))  [#permalink]

### Show Tags

Isn't the tag wrong. It doesnt seem like a 700-level question
_________________

- Stay Hungry, stay Foolish -

Non-Human User Joined: 09 Sep 2013
Posts: 10184
Re: If the function Q is defined by the formula Q = 5w/(4x(z^2))  [#permalink]

### Show Tags

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.
_________________ Re: If the function Q is defined by the formula Q = 5w/(4x(z^2))   [#permalink] 25 Feb 2019, 10:34
Display posts from previous: Sort by

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

 new topic post reply Question banks Downloads My Bookmarks Reviews Important topics Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.  