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 500,000 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 computers, each working at the same constant rate, together can [#permalink]

Show Tags

13 Mar 2011, 10:10

6

This post was BOOKMARKED

00:00

A

B

C

D

E

Difficulty:

15% (low)

Question Stats:

73% (01:54) correct
27% (01:14) wrong based on 189 sessions

HideShow timer Statistics

Six computers, each working at the same constant rate, together can process a certain amount of data in 15 days. How many additional computers, each working at the same constant rate, will be needed to process the same amount of data in 10 days?

Re: Six computers, each working at the same constant rate, together can [#permalink]

Show Tags

13 Mar 2011, 10:11

4. A Explanation: If six computers require 15 days to process the data, thats a total of 90 computer-days the product of 6 and 15. If you change the number of computers or the number of days, 90 will have to remain the product, whether that means 90 days of one computer or one day with 90 computers. In 10 days, the number of computers is: 10c = 90 c = 9 9 computers is 3 more than the 6 that it took to do the job in 15 days, so the correct choice is (A).

...WHAT I DON'T GET, is this business about "90 computer days"... is there another way to solve it? I wouldn't have known at all to solve it the way they solved it

...WHAT I DON'T GET, is this business about "90 computer days"... is there another way to solve it? I wouldn't have known at all to solve it the way they solved it

Number of computers and days taken have an inverse relation. i.e. if number of computers increase, days taken will reduce... Agreed?

If to complete the work in 15 days, you need 6 computers, then to complete the work in 1 day, how many computers will you need? You will need more computers now so you multiply 15 by 6 i.e. 15*6 = 90 computers.

To complete the work in 1 day, you need 90 computers. To complete the work in 10 days, how many computers will you need? You will need fewer computers now, right? So you divide 90 by 10 to get 90/10 = 9 computers. You need 3 extra computers.

Another way: 15 days .................. 6 computers 10 days ...................? computers Unknown is the number of computers. You need to change the previous number of computers to get the new number. You will need to multiply either by 15/10 or 10/15. If you have fewer number of days, you will need more computers so you multiply by 15/10 (i.e. greater than 1) to give a bigger number 6*(15/10) = 9

Another way: Days (d) and computers (c) are inversely proportional. dc = k (a constant) Say x is the new number of computers. 15*6 = k 10*x = k 15*6 = 10*x x = 9

Finally, the given explanation way: 6 computers need 15 days. This means each computer is working for 15 days. How much total work is there? Work which needs 6 computers working simultaneously for 15 days so 15+15+15+15+15+15 = 90 days will be needed if only 1 computer were working. Now, if we need to finish the total work in 10 days, how many computers do we need? 10 + 10 + 10 ..... = 90 We will need 9 such computers to finish the given work.
_________________

Re: Six computers, each working at the same constant rate, together can [#permalink]

Show Tags

20 May 2016, 14:02

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: Six computers, each working at the same constant rate, together can [#permalink]

Show Tags

21 May 2016, 11:08

n2739178 wrote:

Six computers, each working at the same constant rate, together can process a certain amount of data in 15 days. How many additional computers, each working at the same constant rate, will be needed to process the same amount of data in 10 days?

(A) 3 (B) 5 (C) 6 (D) 9 (E) 12

Total work = Computer * Days Total work = 15 * 6 => 90

Quote:

How many additional computers, each working at the same constant rate, will be needed to process the same amount of data in 10 days?

Total work = Computer * Days

90 = Computer * 10

So, Total computers required is 9

So, additional computers required is 3 ( 9 - 6 )

So, Correct answer will be (A) _________________

Thanks and Regards

Abhishek....

PLEASE FOLLOW THE RULES FOR POSTING IN QA AND VA FORUM AND USE SEARCH FUNCTION BEFORE POSTING NEW QUESTIONS

Six computers, each working at the same constant rate, together can [#permalink]

Show Tags

31 May 2016, 03:25

6 computers do work in 15 days, or they do \(\frac{1}{15}\) of the job per day together Thus one computer does \(\frac{1}{15} * \frac{1}{6}\) = \(\frac{1}{90}\) per day

How many computers would we need in total to complete the job in 10 days?

1/ \(\frac{1}{90}\) * X = 10 days \(\frac{90}{X}\) = 10 days 90 = 10X X = 9

In total we need 9 computers to complete the work. Since we already have 6, we need extra 3.
_________________

Please kindly +Kudos if my posts or questions help you!

There’s something in Pacific North West that you cannot find anywhere else. The atmosphere and scenic nature are next to none, with mountains on one side and ocean on...

This month I got selected by Stanford GSB to be included in “Best & Brightest, Class of 2017” by Poets & Quants. Besides feeling honored for being part of...

Joe Navarro is an ex FBI agent who was a founding member of the FBI’s Behavioural Analysis Program. He was a body language expert who he used his ability to successfully...