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

It is currently 22 Feb 2019, 06:27

Close

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
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.

Close

Request Expert Reply

Confirm Cancel
Events & Promotions in February
PrevNext
SuMoTuWeThFrSa
272829303112
3456789
10111213141516
17181920212223
242526272812
Open Detailed Calendar
  • Free GMAT RC Webinar

     February 23, 2019

     February 23, 2019

     07:00 AM PST

     09:00 AM PST

    Learn reading strategies that can help even non-voracious reader to master GMAT RC. Saturday, February 23rd at 7 AM PT
  • FREE Quant Workshop by e-GMAT!

     February 24, 2019

     February 24, 2019

     07:00 AM PST

     09:00 AM PST

    Get personalized insights on how to achieve your Target Quant Score.

In a certain business, production index p is directly proportional to

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

Hide Tags

 
VP
VP
User avatar
D
Joined: 09 Mar 2016
Posts: 1284
Re: In a certain business, production index p is directly proportional to  [#permalink]

Show Tags

New post 24 Aug 2018, 08:03
Bunuel wrote:
gettinit wrote:
Would p be directly proportional to i as well if e is proportional to p? I am thinking it should be, however the constant proportion will be different between p and e and e and i and thus entirely separate between p and i? thanks.


\(a\) is directly proportional to \(b\) means that as the absolute value of \(b\) gets bigger, the absolute value of \(a\) gets bigger too, so there is some non-zero constant \(x\) such that \(a=xb\);

So if \(a\) is directly proportional to \(b\) (\(a=xb\)), then vise-versa is also correct: \(b\) is directly proportional to \(a\) (\(b=\frac{1}{x}*a\) as the absolute value of \(a\) gets bigger, the absolute value of \(b\) gets bigger too).

\(a\) is inversely proportional to \(b\) means that as the absolute value of \(b\) gets bigger, the absolute value of \(a\) gets smaller, so there is some non-zero constant constant \(y\) such that \(a=\frac{y}{b}\).

So if \(a\) is inversely proportional to \(b\) (\(a=\frac{y}{b}\)), then vise-versa is also correct: \(b\) is inversely proportional to \(a\) (\(b=\frac{y}{a}\) as the absolute value of \(a\) gets bigger, the absolute value of \(b\) gets smaller).

As for the question:
In a certain business, production index p is directly proportional to efficiency index e, which is in turn directly proportional to investment i. What is p if i = 70?

Given: \(p=ex\) and \(e=iy\) (for some constants \(x\) and \(y\)), so \(p=ixy\). Question: \(p=70xy=?\) So, basically we should find the value of \(xy\).

(1) e = 0.5 whenever i = 60 --> as \(e=iy\) then \(0.5=60y\) --> we can find the value of \(y\), but still not sufficient.
(2) p = 2.0 whenever i = 50 --> as \(p=ixy\) then \(2=50xy\) --> we can find the value of \(xy\). Sufficient.

Answer: B.

Hope it's clear.



2 = 50
x = 70

Cross Multiply
x = 2.8

is it correct approach ? if not why ?
Manager
Manager
avatar
S
Joined: 05 Nov 2015
Posts: 62
Location: India
Premium Member
Re: In a certain business, production index p is directly proportional to  [#permalink]

Show Tags

New post 24 Aug 2018, 08:37
VeritasKarishma , Bunuel -- is below approach correct ?

What is p if i = 70?

(1) e = 0.5 whenever i = 60 --> no P , n no relation between e & P is established, hence insufficient
(2) p = 2.0 whenever i = 50

(2) if i = 10 --> P = 2/10
if i = 70 --> P = 2/10 *7 --> p=2.8
Manager
Manager
avatar
S
Joined: 05 Nov 2015
Posts: 62
Location: India
Premium Member
In a certain business, production index p is directly proportional to  [#permalink]

Show Tags

New post 24 Aug 2018, 08:40
1
VeritasKarishma , Bunuel -- is below approach correct ?

What is p if i = 70?

(1) e = 0.5 whenever i = 60 --> no P , n no relation between e & P is established, hence insufficient
(2) p = 2.0 whenever i = 50

(2) if i = 10 --> P = 2/10
if i = 70 --> P = 2/10 *7 --> p=2.8
Veritas Prep GMAT Instructor
User avatar
D
Joined: 16 Oct 2010
Posts: 8895
Location: Pune, India
Re: In a certain business, production index p is directly proportional to  [#permalink]

Show Tags

New post 25 Aug 2018, 05:18
s8kadian wrote:
VeritasKarishma , Bunuel -- is below approach correct ?

What is p if i = 70?

(1) e = 0.5 whenever i = 60 --> no P , n no relation between e & P is established, hence insufficient
(2) p = 2.0 whenever i = 50

(2) if i = 10 --> P = 2/10
if i = 70 --> P = 2/10 *7 --> p=2.8


Yes it is fine but you first need to deduce that p is directly proportional to i to solve it this way.
_________________

Karishma
Veritas Prep GMAT Instructor

Learn more about how Veritas Prep can help you achieve a great GMAT score by checking out their GMAT Prep Options >

Intern
Intern
avatar
B
Joined: 02 Jun 2018
Posts: 6
GPA: 3.8
WE: Programming (Computer Software)
Re: In a certain business, production index p is directly proportional to  [#permalink]

Show Tags

New post 06 Nov 2018, 18:21
I agree with this solution, and that is how i interpret Joint variations, However according to the Joint variations article
If x is proportional to y and y is proportional z, then x is inversely proportional to z
x/y=k
y/z=k

Shouldnt
x/yz =constant
and not

xz/y = constant

The article says otherwise.
I cannot tell the difference
GMAT Club Bot
Re: In a certain business, production index p is directly proportional to   [#permalink] 06 Nov 2018, 18:21

Go to page   Previous    1   2   [ 25 posts ] 

Display posts from previous: Sort by

In a certain business, production index p is directly proportional to

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


Copyright

GMAT Club MBA Forum Home| About| Terms and Conditions and Privacy Policy| GMAT Club Rules| Contact| Sitemap

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®.