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

It is currently 09 Dec 2019, 18:39

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

If 6 men can do a piece of work in 30 days of 9 hours each,

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

Hide Tags

Find Similar Topics 
Intern
Intern
avatar
B
Joined: 27 Jul 2011
Posts: 49
If 6 men can do a piece of work in 30 days of 9 hours each,  [#permalink]

Show Tags

New post 15 Jan 2014, 23:50
3
15
00:00
A
B
C
D
E

Difficulty:

  15% (low)

Question Stats:

80% (02:16) correct 20% (02:25) wrong based on 248 sessions

HideShow timer Statistics

If 6 men can do a piece of work in 30 days of 9 hours each, how many men will it take to do 10 times the amount of work if they work for 25 days of 8 hours?

A. 61
B. 64
C. 84
D. 81
E. 94


Please help explains using rates formulae as I could not get the answer. Thanks
Most Helpful Expert Reply
CEO
CEO
User avatar
D
Status: GMATINSIGHT Tutor
Joined: 08 Jul 2010
Posts: 2977
Location: India
GMAT: INSIGHT
Schools: Darden '21
WE: Education (Education)
Reviews Badge
Re: If 6 men can do a piece of work in 30 days of 9 hours each,  [#permalink]

Show Tags

New post 21 Jul 2015, 22:25
6
2
smartyman wrote:
If 6 men can do a piece of work in 30 days of 9 hours each, how many men will it take to do 10 times the amount of work if they work for 25 days of 8 hours?

A. 61
B. 64
C. 84
D. 81
E. 94


Please help explains using rates formulae as I could not get the answer. Thanks


CONCEPT: \(\frac{(Machine_Power * Time)}{Work} = Constant\)

i.e. \(\frac{(M_1 * T_1)}{W_1} = \frac{(M_2 * T_2)}{W_2}\)

i.e. \(\frac{[6 * (30*9)]}{W} = \frac{[M_2 * (25*8)]}{(10*W)}\)

i.e. \(M_2 = 81\)

Answer: option D
_________________
Prosper!!!
GMATinsight
Bhoopendra Singh and Dr.Sushma Jha
e-mail: info@GMATinsight.com I Call us : +91-9999687183 / 9891333772
Online One-on-One Skype based classes and Classroom Coaching in South and West Delhi
http://www.GMATinsight.com/testimonials.html

ACCESS FREE GMAT TESTS HERE:22 ONLINE FREE (FULL LENGTH) GMAT CAT (PRACTICE TESTS) LINK COLLECTION
General Discussion
Director
Director
User avatar
B
Joined: 03 Feb 2013
Posts: 835
Location: India
Concentration: Operations, Strategy
GMAT 1: 760 Q49 V44
GPA: 3.88
WE: Engineering (Computer Software)
Reviews Badge
Re: If 6 men can do a piece of work in 30 days of 9 hours each,  [#permalink]

Show Tags

New post 16 Jan 2014, 02:07
1
2
smartyman wrote:
If 6 men can do a piece of work in 30 days of 9 hours each, how many men will it take to do 10 times the amount of work if they work for 25 days of 8 hours?
A. 61
B. 64
C. 84
D. 81
E. 94


Please help explains using rates formulae as I could not get the answer. Thanks


Amount of work done by 6 men working 30 days working 9 hrs each = 30 * 9 * 6
Let the number of people required for the 2nd case = X

Then X * 25 * 8 = 30 * 9 * 6 * 10
= > X = 81 - Option D)
Veritas Prep GMAT Instructor
User avatar
V
Joined: 16 Oct 2010
Posts: 9859
Location: Pune, India
Re: If 6 men can do a piece of work in 30 days of 9 hours each,  [#permalink]

Show Tags

New post 16 Jan 2014, 21:53
1
smartyman wrote:
If 6 men can do a piece of work in 30 days of 9 hours each, how many men will it take to do 10 times the amount of work if they work for 25 days of 8 hours?

A. 61
B. 64
C. 84
D. 81
E. 94


Please help explains using rates formulae as I could not get the answer. Thanks


Or you can do it using joint variation:

Number of men required = 6 * (30/25) * (9/8) * 10 = 81

Check this link to see how to solve such questions: http://www.veritasprep.com/blog/2013/02 ... variation/
_________________
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
Status: Preparing for GMAT
Joined: 10 Dec 2013
Posts: 13
Location: India
Concentration: Marketing, Leadership
GMAT 1: 530 Q46 V18
WE: Other (Entertainment and Sports)
Re: If 6 men can do a piece of work in 30 days of 9 hours each,  [#permalink]

Show Tags

New post 18 Jul 2014, 04:21
Can someone please explain any other method, preferably the w=rt method. Work rate problems always seem so simple but I always go wrong or am stuck. I was not able to grasp it even after going through the two approaches. Thank you.
Director
Director
User avatar
S
Joined: 17 Dec 2012
Posts: 623
Location: India
If 6 men can do a piece of work in 30 days of 9 hours each,  [#permalink]

Show Tags

New post 18 Jul 2014, 04:38
In this type of problems, converting for unit values will make it easy to solve.

Take a look at the first sentence. We can say, to do the work in 1 day of 9 hours each will take 6*30 men.
To do the work in 25 days will take (6*30) /25 men
Similarly adding the info, that to do the work in a day of 8 hours instead of 9 hours each will take (6 *30*9)/ (25*8) men
To do 10 times the amount of work will take 10 * (6*30*9) / (25*8) = 81 men
_________________
Srinivasan Vaidyaraman
Sravna Test Prep
http://www.sravnatestprep.com

Holistic and Systematic Approach
VP
VP
avatar
P
Joined: 07 Dec 2014
Posts: 1217
Re: If 6 men can do a piece of work in 30 days of 9 hours each,  [#permalink]

Show Tags

New post 25 Sep 2016, 13:06
If 6 men can do a piece of work in 30 days of 9 hours each, how many men will it take to do 10 times the amount of work if they work for 25 days of 8 hours?

A. 61
B. 64
C. 84
D. 81
E. 94

6*30*9=1620 total man hours to do work
let m=number of men needed
m*25*8*1/1620=10
m=81 men
D.
Senior SC Moderator
avatar
V
Joined: 22 May 2016
Posts: 3729
If 6 men can do a piece of work in 30 days of 9 hours each,  [#permalink]

Show Tags

New post 30 Nov 2017, 13:56
smartyman wrote:
If 6 men can do a piece of work in 30 days of 9 hours each, how many men will it take to do 10 times the amount of work if they work for 25 days of 8 hours?

A. 61
B. 64
C. 84
D. 81
E. 94

Please help explains using rates formulae as I could not get the answer. Thanks

One version of the rate formula approach . . .
Use standard W = RT formula, but add (# of workers or machines) to R*T, thus: W = #*R*T

Work = (# of workers) * individual rate * time

Scenario 1

Get individual rate from first scenario, where t = (30 * 9hrs = 270 hrs)

Work = # * r * t

1 = 6 * ?? * 270

1 = r * 1620

r = \(\frac{1}{1620}\)

Scenario 2

At that rate, how many men will it take to do 10 times the amount of work if they work for 25 days of 8 hours?
t = (25 * 8 hrs = 200 hrs)

Work = # * r * t

10 = ?? * \(\frac{1}{1620}\) * 200

10 = # * \(\frac{200}{1620}\)

# of workers = \(\frac{10}{(\frac{200}{1620})} =\)

# of workers =\((10 * \frac{1620}{200})=(\frac{1620}{20})=\frac{162}{2}= 81\)

Answer D
_________________
SC Butler has resumed! Get two SC questions to practice, whose links you can find by date, here.

Never doubt that a small group of thoughtful, committed citizens can change the world; indeed, it's the only thing that ever has -- Margaret Mead
Target Test Prep Representative
User avatar
V
Status: Founder & CEO
Affiliations: Target Test Prep
Joined: 14 Oct 2015
Posts: 8647
Location: United States (CA)
Re: If 6 men can do a piece of work in 30 days of 9 hours each,  [#permalink]

Show Tags

New post 01 Dec 2017, 07:49
smartyman wrote:
If 6 men can do a piece of work in 30 days of 9 hours each, how many men will it take to do 10 times the amount of work if they work for 25 days of 8 hours?

A. 61
B. 64
C. 84
D. 81
E. 94


The hourly rate of the 6 men is 1/(30 x 9) = 1/270. If we let x = the number of men needed to do 10 times the work when they work for 25 days of 8 hours, then the hourly rate of these x men must be 10/(25 x 8) = 10/200 = 1/20. We can create the following proportion and solve for x:

6/(1/270) = x/(1/20)

1620 = 20x

x = 1620/20 = 81

Answer: D
_________________

Scott Woodbury-Stewart

Founder and CEO

Scott@TargetTestPrep.com
TTP - Target Test Prep Logo
122 Reviews

5-star rated online GMAT quant
self study course

See why Target Test Prep is the top rated GMAT quant course on GMAT Club. Read Our Reviews

If you find one of my posts helpful, please take a moment to click on the "Kudos" button.

Intern
Intern
avatar
B
Joined: 28 Sep 2011
Posts: 14
Location: India
GMAT 1: 640 Q47 V31
GMAT 2: 640 Q47 V31
GPA: 3
GMAT ToolKit User
If 6 men can do a piece of work in 30 days of 9 hours each,  [#permalink]

Show Tags

New post 29 Nov 2019, 06:35
The best way to tackle any of these problems is to follow this sequence (be it any question)

No. of workers ----- Time ----- work
6 ----- 30x9 hrs ----- 1

we need to find:

? ----- 25x8 ----- 10

so, by unitary method:

6 ----- 1 ----- 1/ (30x9)

1 ----- 1 ----- 1/ (30x9)*(6)

1 ----- 25x8 ----- 25x8/ (30x9)*(6)

so,

{(10)* (30x9)*(6)/ (25x8)} ----- 25x8 ----- 10
=81
GMAT Club Bot
If 6 men can do a piece of work in 30 days of 9 hours each,   [#permalink] 29 Nov 2019, 06:35
Display posts from previous: Sort by

If 6 men can do a piece of work in 30 days of 9 hours each,

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





Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne