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.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 350,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

Six machines, each working at the same constant rate [#permalink]
26 Apr 2010, 20:53

2

This post was BOOKMARKED

00:00

A

B

C

D

E

Difficulty:

5% (low)

Question Stats:

82% (01:48) correct
18% (01:05) wrong based on 337 sessions

Six machines, each working at the same constant rate, together can complete a certain job in 12 days. How many additional machines, each working at the same constant rate, will be needed to complete the Job in 8 days?

Re: Six machines, each working at the same constant rate [#permalink]
26 Apr 2010, 21:50

1

This post received KUDOS

zz0vlb wrote:

Six machines, each working at the same constant rate, together can complete a certain job in 12 days. How many additional machines, each working at the same constant rate, will be needed to complete the Job in 8 days? a.2 b.3 c.4 d.6 e.8

let each machine work at rate of x days 1/x+1/x+1/x+1/x+1/x+1/x = 1/12 6/x = 1/12 x = 72 now y is number of machines needed to complete job in 8 days so, y/72 = 1/8 y = 9 required = y-x = 3 hence b.

Re: Six machines, each working at the same constant rate [#permalink]
27 Apr 2010, 05:02

3

This post received KUDOS

zz0vlb wrote:

Six machines, each working at the same constant rate, together can complete a certain job in 12 days. How many additional machines, each working at the same constant rate, will be needed to complete the Job in 8 days?

Another solution which is faster is Since each machine works at a constant rate. The time needs to bought down from 12 to 8. So the new time is 2/3 of the original time. Thus to achieve this we need the rate to be 3/2 of original.

So 3/2* 6 = 9

So we need 9-6 = 3 more machines. _________________

Six machines, each working at the same constant rate, together can complete a certain job in 12 days. How many additional machines, each working at the same constant rate, will be needed to complete the job in 8 days?

A. 2 B. 3 C. 4 D. 6 E. 8

Let \(x\) be the time needed for 1 machine to complete the job, so rate of one machine is \(\frac{1}{x}\) (rate is the reciprocal of time) --> rate of 6 machines would be \(\frac{6}{x}\).

As \(job=time*rate\) --> \(1=12*\frac{6}{x}\) --> \(x=72\) days needed for 1 machine to complete the job.

To complete the job in 8 days \(\frac{72}{8}=9\) machines are needed.

Another solution which is faster is Since each machine works at a constant rate. The time needs to bought down from 12 to 8. So the new time is 2/3 of the original time. Thus to achieve this we need the rate to be 3/2 of original.

So 3/2* 6 = 9

So we need 9-6 = 3 more machines. _________________

Re: Six machines, each working at the same constant rate [#permalink]
19 Jun 2010, 18:52

2

This post received KUDOS

Actually, this was more simple than I thought. When I first saw this, I started to panic thinking it's a rate question. But then I took a step back, and it was the simplest of calculations.

So here's the deal:

12 days -> 6 machines: 8 days -> ?

8 days means you definitely need more machines than the 6 and in such case the equation looks like-

Re: GMAT PREP (PS) [#permalink]
18 Jun 2011, 17:56

Lets look at this way :As the rate of one machine is constant i e 1/(12*6)=1/72 .Even after addition of extra machines the rate will remain the same .Hence,if machines are x now ,the rate becomes 1/8x which is equal to 1/72. X comes out to be 9 . Machines added=9-6=3 _________________

Re: GMAT PREP (PS) [#permalink]
05 Aug 2011, 12:17

6 machines 12 days... therefore (6*12)/8=9number of machines required to complete the job in 8 days Therefore additional machines required=9-6=3 Answer is B _________________

Hi, can someone tell me if this is really a level 700 question? I felt like this was so much easier than some of the other questions posted but its labelled as level 700.

Hi, can someone tell me if this is really a level 700 question? I felt like this was so much easier than some of the other questions posted but its labelled as level 700.

Yes its definitely not a 700 level question but then rating of a question on a forum is as per the poster. A 700 level question for me can look like a 500 for you and vice-versa. I would rather concentrate on the take aways from each question

I am the master of my fate. I am the captain of my soul. Please consider giving +1 Kudos if deserved!

DS - If negative answer only, still sufficient. No need to find exact solution. PS - Always look at the answers first CR - Read the question stem first, hunt for conclusion SC - Meaning first, Grammar second RC - Mentally connect paragraphs as you proceed. Short = 2min, Long = 3-4 min

Re: Six machines, each working at the same constant rate [#permalink]
03 Mar 2013, 23:09

zz0vlb wrote:

Six machines, each working at the same constant rate, together can complete a certain job in 12 days. How many additional machines, each working at the same constant rate, will be needed to complete the Job in 8 days?

Re: Six machines, each working at the same constant rate [#permalink]
24 Dec 2014, 05:20

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. _________________

safe.txmblr Can business make a difference in the great problems that we face? My own view is nuanced. I think business potentially has a significant role to play...

Still 7 months to go to be at Lausanne. But, as Lausanne has a vacancy rate of 0.1% for rental properties, I booked my rental apartment yesterday for...