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

It is currently 20 Sep 2018, 00:08

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

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

Director
Director
User avatar
P
Joined: 09 Mar 2016
Posts: 863
Re: In a certain business, production index p is directly proportional to  [#permalink]

Show Tags

New post 24 Aug 2018, 09:03
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 ?
_________________

In English I speak with a dictionary, and with people I am shy.

Manager
Manager
avatar
S
Joined: 05 Nov 2015
Posts: 70
Location: India
In a certain business, production index p is directly proportional to  [#permalink]

Show Tags

New post 24 Aug 2018, 09:40
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
P
Joined: 16 Oct 2010
Posts: 8281
Location: Pune, India
Re: In a certain business, production index p is directly proportional to  [#permalink]

Show Tags

New post 25 Aug 2018, 06:18
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 >

GMAT self-study has never been more personalized or more fun. Try ORION Free!

Re: In a certain business, production index p is directly proportional to &nbs [#permalink] 25 Aug 2018, 06:18

Go to page   Previous    1   2   [ 24 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  

Events & Promotions

PREV
NEXT


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®.