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

It is currently 16 Dec 2018, 07:14

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 December
PrevNext
SuMoTuWeThFrSa
2526272829301
2345678
9101112131415
16171819202122
23242526272829
303112345
Open Detailed Calendar
  • Free GMAT Prep Hour

     December 16, 2018

     December 16, 2018

     03:00 PM EST

     04:00 PM EST

    Strategies and techniques for approaching featured GMAT topics
  • FREE Quant Workshop by e-GMAT!

     December 16, 2018

     December 16, 2018

     07:00 AM PST

     09:00 AM PST

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

Three machines operating independently, simultaneously, and

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

Hide Tags

Intern
Intern
avatar
Joined: 24 Oct 2011
Posts: 5
Schools: Sloan '16 (M)
Three machines operating independently, simultaneously, and  [#permalink]

Show Tags

New post 09 Oct 2013, 18:23
4
35
00:00
A
B
C
D
E

Difficulty:

  25% (medium)

Question Stats:

74% (00:52) correct 26% (00:50) wrong based on 1068 sessions

HideShow timer Statistics

Three machines operating independently, simultaneously, and at the same constant rate can fill a certain production order in 36 hours. If one additional machine were used under the same operating conditions, in how many fewer hours of simultaneous operation could the production order be fulfilled?

A. 6
B. 9
C. 12
D. 27
E. 48
Most Helpful Expert Reply
EMPOWERgmat Instructor
User avatar
V
Status: GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 13095
Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: Q170 V170
Re: Three machines operating independently, simultaneously, and  [#permalink]

Show Tags

New post 12 Feb 2015, 11:55
16
7
Hi All,

These type of "work" questions can be solved in a variety of ways (depending on how you want to do the math).

Since we have 3 machines, each of which works for 36 hours to complete a job, we know that....

(3 machines)(36 hours each) = 108 machine-hours are needed to complete the job.

Since we're told that all the machines work at the same rate, adding a 4th machine is not going to be difficult to deal with. The 108 machine-hours are still needed to complete the job, but now we have 4 machines doing work instead of 3...

(108 machine-hours)/(4 machines) = 27 hours.

Since the original time was 36 hours and the "new" time is 27 hours, the difference is 9 hours.

Final Answer:

GMAT assassins aren't born, they're made,
Rich
_________________

760+: Learn What GMAT Assassins Do to Score at the Highest Levels
Contact Rich at: Rich.C@empowergmat.com

Rich Cohen

Co-Founder & GMAT Assassin

Special Offer: Save $75 + GMAT Club Tests Free
  Official GMAT Exam Packs + 70 Pt. Improvement Guarantee
www.empowergmat.com/

*****Select EMPOWERgmat Courses now include ALL 6 Official GMAC CATs!*****

Most Helpful Community Reply
Manager
Manager
avatar
Joined: 30 May 2013
Posts: 158
Location: India
Concentration: Entrepreneurship, General Management
GPA: 3.82
GMAT ToolKit User
Re: Three machines operating independently, simultaneously, and  [#permalink]

Show Tags

New post 10 Oct 2013, 03:39
10
7
Hi,

all 3 machine works at same rate = 1/x

1/x + 1/x + 1/x = 1/36
3/x = 1/36
x = 108.

Fourth machine was used with same rate (1/x)
Total Rate for 4 MAchines
= 4/x
=4/108
=1/27 is the over all rate of four machine
So time is 1/Rate = 27 hrs

Question asked was "how many fewer hours of simultaneous operation could the production order be fulfilled"
so 36 - 27 = 9 Hrs
General Discussion
Manager
Manager
avatar
Joined: 10 Jan 2011
Posts: 146
Location: India
GMAT Date: 07-16-2012
GPA: 3.4
WE: Consulting (Consulting)
Reviews Badge
Re: Three machines operating independently, simultaneously, and  [#permalink]

Show Tags

New post 10 Oct 2013, 00:33
5
If 3 Machines can do the work in 36 hr then 4 Machines can do the work in 3/4*36 = 27 Hrs. hence time saved will be 9hr

option B is the correct answer
_________________

-------Analyze why option A in SC wrong-------

Manager
Manager
avatar
Joined: 26 Feb 2012
Posts: 100
Location: India
Concentration: General Management, Finance
WE: Engineering (Telecommunications)
Re: Three machines operating independently, simultaneously, and  [#permalink]

Show Tags

New post 06 Feb 2014, 09:09
3
3 Machines 36 hr
1 Machines 108 hrs
4 machines 27 hrs

Now 36-27=9 hrs fewer......B

Rgds
Prasannajeet
Intern
Intern
avatar
Joined: 01 Aug 2006
Posts: 33
Re: Three machines operating independently, simultaneously, and  [#permalink]

Show Tags

New post 07 Feb 2014, 20:37
1
1
3 -> 36
4 -> x
Because they are inversely related, 4x = 3*36 => x = 27.
36-9 = 27.
Manager
Manager
avatar
Joined: 06 Jun 2014
Posts: 90
Location: United States
Concentration: Finance, General Management
GMAT 1: 450 Q27 V21
GPA: 3.47
GMAT ToolKit User
Re: Three machines operating independently, simultaneously, and  [#permalink]

Show Tags

New post 17 Jul 2016, 11:48
1
kiseki wrote:
Three machines operating independently, simultaneously, and at the same constant rate can fill a certain production order in 36 hours. If one additional machine were used under the same operating conditions, in how many fewer hours of simultaneous operation could the production order be fulfilled?

A. 6
B. 9
C. 12
D. 27
E. 48


\(\frac{36}{3}=\) 12 hours (each machine take 12 hours)
(3 machines * 12 hours) = (4 machines take x hours)
12 * 3 = 4 * X
36 = 4x
9 = x
4 machines will take 9 hours less to finish the same order
Answer B
_________________

1) Kaplanprep 450 Q27 V21
2) Manhattan 530 Q35 V28
3) GmatPrep 450 Q33, V19
4) Veritas 460 Q31, V23
5) Veritas 440 Q 30, V21
6) Veritas 500 Q34, V 25
7) Gmat 420 Q27, V23
8) Veritas 520 Q36, V26 2/2
9) Veritas 540 Q37, V28 4/19
10)Manhattan 560 Q40, V28 4/28

Manager
Manager
avatar
B
Joined: 23 Dec 2013
Posts: 150
Location: United States (CA)
GMAT 1: 710 Q45 V41
GMAT 2: 760 Q49 V44
GPA: 3.76
Reviews Badge
Re: Three machines operating independently, simultaneously, and  [#permalink]

Show Tags

New post 22 Jul 2017, 18:03
kiseki wrote:
Three machines operating independently, simultaneously, and at the same constant rate can fill a certain production order in 36 hours. If one additional machine were used under the same operating conditions, in how many fewer hours of simultaneous operation could the production order be fulfilled?

A. 6
B. 9
C. 12
D. 27
E. 48


Let C = the rate of one of the machines

3C = 1/36
C = 1/(36*3)

Add one more machine to determine the net impact...

4C = 4/(36*3) = 1/(9+3)

It would take 4 machines 27 hours to finish the job.

36-27 = 9 hours.
Intern
Intern
avatar
B
Joined: 19 Jun 2017
Posts: 4
GMAT 1: 720 Q49 V38
Re: Three machines operating independently, simultaneously, and  [#permalink]

Show Tags

New post 07 Aug 2017, 08:27
Use inverse proportion concept to solve it quickly.

Initial number of machines=3
New Number of machines=4(after adding one more machine)

So number of machines increases by 1/3 of the initial number

Since time taken will be inversely proportional to the number of machines, therefore if number of machines increases by 1/3, time taken decrease by 1/4

1/4 of 36 = 9.

Therefore B
Manager
Manager
avatar
B
Joined: 24 Jun 2017
Posts: 122
Re: Three machines operating independently, simultaneously, and  [#permalink]

Show Tags

New post 07 Aug 2017, 11:10
a usual approach for work rate problems

3 machines, same productivity rate do some work in 36 hours, so mount of work is 108
if 1 more machine with the same rate is added then:

108 = 4*x
x = 27
Question asks "how many fewer hours" so we subtract 27 from initial 36 = 9
Manager
Manager
avatar
S
Joined: 24 Sep 2018
Posts: 138
Premium Member CAT Tests
Re: Three machines operating independently, simultaneously, and  [#permalink]

Show Tags

New post 17 Oct 2018, 10:56
Attachment:
Screen Shot 2018-10-18 at 12.23.32 AM.png
Screen Shot 2018-10-18 at 12.23.32 AM.png [ 38.2 KiB | Viewed 2755 times ]
If time taken by 4 machines is 27 hrs
Time taken by 3 machines is 36 hrs.
Question asks: how many fewer hours of simultaneous operation could the production order be fulfilled?
36-27 = 9 hrs
Same work would take 9 fewer hours.
_________________

Please award :thumbup: kudos, If this post helped you in someway. :student_man:

Manager
Manager
avatar
B
Joined: 28 Jun 2018
Posts: 66
Re: Three machines operating independently, simultaneously, and  [#permalink]

Show Tags

New post 12 Nov 2018, 00:57
Easiest way:

4x30 = 5x
x= 24

Fewer hours : 36-27

Answer 9.
Manager
Manager
avatar
S
Joined: 01 Mar 2015
Posts: 76
Re: Three machines operating  [#permalink]

Show Tags

New post 24 Nov 2018, 21:49
shrik wrote:
Three machines operating independently, simultaneously, and at the same constant rate can fill a certain production order in 36 hours. If one additional machine were used under the same operating conditions, in how many fewer hours of simultaneous operation could the production order be filled?

6
9
12
27
48


Total machine hours= 3 * 36 = 108
Now, no. of machines = 4
Total work hours will be same
Therefore, work can be completed in hours = total hours/ no. of machines
= 108/4 = 27 hours

Answer choice (D)

Posted from my mobile device
VP
VP
User avatar
V
Status: It's near - I can see.
Joined: 13 Apr 2013
Posts: 1355
Location: India
Concentration: International Business, Operations
GMAT 1: 480 Q38 V22
GPA: 3.01
WE: Engineering (Consulting)
Premium Member Reviews Badge CAT Tests
Re: Three machines operating  [#permalink]

Show Tags

New post 24 Nov 2018, 22:16
shrik wrote:
Three machines operating independently, simultaneously, and at the same constant rate can fill a certain production order in 36 hours. If one additional machine were used under the same operating conditions, in how many fewer hours of simultaneous operation could the production order be filled?

6
9
12
27
48


Total no. of working hours of all the 3 machines = 3 * 36 = 108 hours

We add one more machine, but work will remain the same,

So new working hours completed by each machine = 108/4 = 27 hours

We want to know the difference between hours used in first and the second attempt,

Therefore, 36 - 27 = 9 (B)



Alternatively,

3 * 36 = Work ---- (I)

4 * X = Work ------(II)

Where X is no. of working hours when one machine is added.

From I and II,

3 * 36 = 4 * X

X = 27 hours

Difference = 36 - 27 = 9 hours (B)

_________________

"Do not watch clock; Do what it does. KEEP GOING."

VP
VP
User avatar
D
Joined: 09 Mar 2016
Posts: 1234
Three machines operating independently, simultaneously, and  [#permalink]

Show Tags

New post 25 Nov 2018, 08:00
kiseki wrote:
Three machines operating independently, simultaneously, and at the same constant rate can fill a certain production order in 36 hours. If one additional machine were used under the same operating conditions, in how many fewer hours of simultaneous operation could the production order be fulfilled?

A. 6
B. 9
C. 12
D. 27
E. 48



since the amount of work completed is the same, weather it will be 4 or 6 machines, I made following equation

total machines/ hours \(36*3 = 108\)


\((36-x)*4= 108\)

\(144-4x=108\)

\(4x =36\)

\(x = 9\)

So 9 hours fewer :)
GMATH Teacher
User avatar
G
Status: GMATH founder
Joined: 12 Oct 2010
Posts: 546
Re: Three machines operating independently, simultaneously, and  [#permalink]

Show Tags

New post 25 Nov 2018, 12:01
kiseki wrote:
Three machines operating independently, simultaneously, and at the same constant rate can fill a certain production order in 36 hours. If one additional machine were used under the same operating conditions, in how many fewer hours of simultaneous operation could the production order be fulfilled?

A. 6
B. 9
C. 12
D. 27
E. 48

\(? = \left( {{\rm{time}}\,\,3\,\,{\rm{mach}}{\rm{.}}\,\,{\rm{together}}} \right) - \left( {{\rm{time}}\,\,4\,\,{\rm{mach}}{\rm{.}}\,\,{\rm{together}}} \right)\,\, = \,\,36\,\, - \,\,{?_{{\rm{temp}}}}\,\,\,\,\,\,\left[ {\rm{h}} \right]\)

\({\rm{each}}\,\,{\rm{mach}}{\rm{.}}\,\,{\rm{alone}}\,\,\, \to \,\,\,3 \cdot 36\,\,{\rm{h}}\,\,\,\,\,\, \Rightarrow \,\,\,\,\,\,\,{?_{{\rm{temp}}}}\,\, = \,\,\,{{3 \cdot 36} \over 4}\,\,{\rm{h}}\,\,{\rm{ = }}\,\,27\,{\rm{h}}\)

\(? = 36 - 27 = \,\,9\,\,\,\left[ {\rm{h}} \right]\)


This solution follows the notations and rationale taught in the GMATH method.

Regards,
Fabio.
_________________

Fabio Skilnik :: https://GMATH.net (Math for the GMAT) or GMATH.com.br (Portuguese version)
Course release PROMO : finish our test drive till 30/Dec with (at least) 50 correct answers out of 92 (12-questions Mock included) to gain a 50% discount!

GMAT Club Bot
Re: Three machines operating independently, simultaneously, and &nbs [#permalink] 25 Nov 2018, 12:01
Display posts from previous: Sort by

Three machines operating independently, simultaneously, and

  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®.