Summer is Coming! Join the Game of Timers Competition to Win Epic Prizes. Registration is Open. Game starts Mon July 1st.

 It is currently 18 Jul 2019, 15:29 ### 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.  # In the equation 3r^{4}=(2/s), if r is doubled, then s must be

Author Message
TAGS:

### Hide Tags

Intern  Joined: 30 Mar 2015
Posts: 14
GMAT 1: 730 Q49 V40 In the equation 3r^{4}=(2/s), if r is doubled, then s must be  [#permalink]

### Show Tags

2
10 00:00

Difficulty:   45% (medium)

Question Stats: 67% (01:22) correct 33% (01:33) wrong based on 284 sessions

### HideShow timer Statistics In the equation $$3r^{4}$$=$$\frac{2}{s}$$, if r is doubled, the s must be multiplied by:

A.$$\frac{1}{16}$$

B. $$\frac{1}{8}$$

C.$$\frac{1}{4}$$

D. 4

E. 16

Originally posted by petu on 14 Jun 2015, 08:26.
Last edited by petu on 14 Jun 2015, 08:35, edited 1 time in total.
Veritas Prep GMAT Instructor D
Joined: 16 Oct 2010
Posts: 9446
Location: Pune, India
Re: In the equation 3r^{4}=(2/s), if r is doubled, then s must be  [#permalink]

### Show Tags

2
4
irus wrote:
why 1/16 can someone explain pls

$$3*r^4 = \frac{2}{s}$$
$$s= \frac{2}{3*r^4}$$ (multiply by s and divide by 3r^4)

What happens when r becomes 2r.

You get $$\frac{2}{3(2*r)^4} = \frac{2}{3*16*r^4}$$

How is this new expression different from the old one? The new one = Old one * (1/16)

Hence, s gets multiplied by 1/16 when r becomes twice.
_________________
Karishma
Veritas Prep GMAT Instructor

##### General Discussion
Math Expert V
Joined: 02 Sep 2009
Posts: 56257
Re: In the equation 3r^{4}=(2/s), if r is doubled, then s must be  [#permalink]

### Show Tags

petu wrote:
In the equation $$3r^{4}$$=$$\frac{2}{s}$$, if r is doubled, the s must be multiplied by:

A.$$\frac{1}{16}$$

B. $$\frac{1}{8}$$

C.$$\frac{1}{4}$$

D. 4

E. 16

Similar question to practice: if-the-function-q-is-defined-by-the-formula-q-5w-4x-z-131051.html
_________________
Intern  Joined: 07 Aug 2014
Posts: 7
Re: In the equation 3r^{4}=(2/s), if r is doubled, then s must be  [#permalink]

### Show Tags

1
just plug in a number for r , like 1

Then solve for s , once you have s, all you have to do is double the value of r (which will now be: 2) , then solve for the new value of y
Director  V
Joined: 27 May 2012
Posts: 816
Re: In the equation 3r^{4}=(2/s), if r is doubled, then s must be  [#permalink]

### Show Tags

VeritasPrepKarishma wrote:
irus wrote:
why 1/16 can someone explain pls

$$3*r^4 = \frac{2}{s}$$
$$s= \frac{2}{3*r^4}$$ (multiply by s and divide by 3r^4)

What happens when r becomes 2r.

You get $$\frac{2}{3(2*r)^4} = \frac{2}{3*16*r^4}$$

How is this new expression different from the old one? The new one = Old one * (1/16)

Hence, s gets multiplied by 1/16 when r becomes twice.

Hi Karishma,

I have a small doubt here , I kept r to the left and s to the right and worked at it that way , below is the working :

Given $$3 r^4 = \frac {2}{s}$$
now r is doubled

$$(2r)^4 =\frac{2}{3s}$$
$$16r^4= \frac{2}{3s}$$

Now the above can be rearranged as $$3r^4= \frac{2}{16s}$$
on comparing this with the original it seemed that s is being multiplied by 16 when r is doubled , hence I chose E. What is the error in the logic here?
_________________
- Stne
Veritas Prep GMAT Instructor D
Joined: 16 Oct 2010
Posts: 9446
Location: Pune, India
Re: In the equation 3r^{4}=(2/s), if r is doubled, then s must be  [#permalink]

### Show Tags

stne wrote:
VeritasPrepKarishma wrote:
irus wrote:
why 1/16 can someone explain pls

$$3*r^4 = \frac{2}{s}$$
$$s= \frac{2}{3*r^4}$$ (multiply by s and divide by 3r^4)

What happens when r becomes 2r.

You get $$\frac{2}{3(2*r)^4} = \frac{2}{3*16*r^4}$$

How is this new expression different from the old one? The new one = Old one * (1/16)

Hence, s gets multiplied by 1/16 when r becomes twice.

Hi Karishma,

I have a small doubt here , I kept r to the left and s to the right and worked at it that way , below is the working :

Given $$3 r^4 = \frac {2}{s}$$
now r is doubled

$$(2r)^4 =\frac{2}{3s}$$
$$16r^4= \frac{2}{3s}$$

Now the above can be rearranged as $$3r^4= \frac{2}{16s}$$
on comparing this with the original it seemed that s is being multiplied by 16 when r is doubled , hence I chose E. What is the error in the logic here?

s is in the denominator. You cannot say what it multiplies by.
To know "s is multiplied by ...", you need to separate out the s.
s = Old expression
New s = m * Old expression
You need the value of m.
_________________
Karishma
Veritas Prep GMAT Instructor Re: In the equation 3r^{4}=(2/s), if r is doubled, then s must be   [#permalink] 24 Feb 2018, 05:17
Display posts from previous: Sort by

# In the equation 3r^{4}=(2/s), if r is doubled, then s must be   