Author 
Message 
TAGS:

Hide Tags

Manager
Status: Persevere
Joined: 08 Jan 2016
Posts: 114
Location: Hong Kong
GPA: 3.52

Five machines at a certain factory operate at the same constant rate
[#permalink]
Show Tags
24 May 2016, 22:19
Question Stats:
74% (01:30) correct 26% (01:41) wrong based on 1317 sessions
HideShow timer Statistics
Five machines at a certain factory operate at the same constant rate. If four of these machines, operating simultaneously, take 30 hours to fill a certain production order, how many fewer hours does it take all five machines, operating simultaneously, to fill the same production order? (A) 3 (B) 5 (C) 6 (D) 16 (E) 24
Official Answer and Stats are available only to registered users. Register/ Login.




Math Expert
Joined: 02 Aug 2009
Posts: 8283

Re: Five machines at a certain factory operate at the same constant rate
[#permalink]
Show Tags
25 May 2016, 06:34
nalinnair wrote: Five machines at a certain factory operate at the same constant rate. If four of these machines, operating simultaneously, take 30 hours to fill a certain production order, how many fewer hours does it take all five machines, operating simultaneously, to fill the same production order?
(A) 3 (B) 5 (C) 6 (D) 16 (E) 24 4 machines do a work in 30 days.. 1 machine will do that work in 30*4 days... 5 machines will do it in \(30*\frac{4}{5}= 24..\) lesser time = \(3024 = 6\) C
_________________




Marshall & McDonough Moderator
Joined: 13 Apr 2015
Posts: 1675
Location: India

Re: Five machines at a certain factory operate at the same constant rate
[#permalink]
Show Tags
25 May 2016, 00:19
Total work done by 4 machines = 30 * 4 = 120 units
When one more machine is added each machine works for > 120/5 = 24 hours
Difference = 30  24 = 6hrs
Answer: C




Board of Directors
Status: QA & VA Forum Moderator
Joined: 11 Jun 2011
Posts: 4849
Location: India
GPA: 3.5
WE: Business Development (Commercial Banking)

Re: Five machines at a certain factory operate at the same constant rate
[#permalink]
Show Tags
25 May 2016, 06:43
nalinnair wrote: Five machines at a certain factory operate at the same constant rate. If four of these machines, operating simultaneously, take 30 hours to fill a certain production order, how many fewer hours does it take all five machines, operating simultaneously, to fill the same production order?
(A) 3 (B) 5 (C) 6 (D) 16 (E) 24 Total work = 4*30 machine hrs Time taken = 4* 30 /5 => 24 hours... Thus all five machines, operating simultaneously will take ( 30  24 ) 6 hours.. Answer will be (C) 6
_________________



Current Student
Joined: 18 Oct 2014
Posts: 786
Location: United States
GPA: 3.98

Re: Five machines at a certain factory operate at the same constant rate
[#permalink]
Show Tags
25 May 2016, 07:40
nalinnair wrote: Five machines at a certain factory operate at the same constant rate. If four of these machines, operating simultaneously, take 30 hours to fill a certain production order, how many fewer hours does it take all five machines, operating simultaneously, to fill the same production order?
(A) 3 (B) 5 (C) 6 (D) 16 (E) 24 If 4 machines take 30 hrs, 5 machines will take 30*4/5= 24 hrs How many fewer hours will all five machines take= 3024= 6 hrs C is the answer
_________________
I welcome critical analysis of my post!! That will help me reach 700+



Manager
Joined: 08 Nov 2015
Posts: 54

Re: Five machines at a certain factory operate at the same constant rate
[#permalink]
Show Tags
07 Jan 2017, 23:50
nalinnair wrote: Five machines at a certain factory operate at the same constant rate. If four of these machines, operating simultaneously, take 30 hours to fill a certain production order, how many fewer hours does it take all five machines, operating simultaneously, to fill the same production order?
(A) 3 (B) 5 (C) 6 (D) 16 (E) 24 Let the rate of machine be x hours. So in hour it can complete 1/x of work. Four machine rate = 4*(1/x) = 4/x. Now, Rate* Time = Job i.e. 4/x*30 = Job. So one machine can take 120 hour to complete the job. Five machine works together it can take :120/5 = 24 hours to complete the job. Hence 3024 = 6 hours. Answer is C.



IIMA, IIMC School Moderator
Joined: 04 Sep 2016
Posts: 1386
Location: India
WE: Engineering (Other)

Five machines at a certain factory operate at the same constant rate
[#permalink]
Show Tags
20 May 2018, 19:29
Hi VeritasPrepKarishma chetan2u niks18 gmatbusters BunuelLet me know if my below approach is correct using 'Joint variation' as discussed hereI have to find number of hrs when machines operating are increased from 4 to 5. Simple logic says if I increase the no of machines, the no of hrs to complete the same work will be reduced. Hence if I have initial no. of hrs defined, I need to multiply it by proper fraction ie numerator/denominator < 1 Using above steps: No of hrs = 30 (when 4 machines are operational) I need to multiply this by 4/5 since I need a fraction less than 1. Hence I get 30 * (4/5) = 24 as hrs required when 5 machines are operational. I already know that when 4 machines are working, I shall need 30 hrs. Hence, difference = 3024 ie 6 hrs.
_________________
It's the journey that brings us happiness not the destination. Feeling stressed, you are not alone!!



Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 10097
Location: Pune, India

Re: Five machines at a certain factory operate at the same constant rate
[#permalink]
Show Tags
20 May 2018, 19:38
adkikani wrote: Hi VeritasPrepKarishma chetan2u niks18 gmatbusters BunuelLet me know if my below approach is correct using 'Joint variation' as discussed hereI have to find number of hrs when machines operating are increased from 4 to 5. Simple logic says if I increase the no of machines, the no of hrs to complete the same work will be reduced. Hence if I have initial no. of hrs defined, I need to multiply it by proper fraction ie numerator/denominator < 1 Using above steps: No of hrs = 30 (when 4 machines are operational) I need to multiply this by 4/5 since I need a fraction less than 1. Hence I get 30 * (4/5) = 24 as hrs required when 5 machines are operational. I already know that when 4 machines are working, I shall need 30 hrs. Hence, difference = 3024 ie 6 hrs. Yes, absolutely correct.
_________________
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 >



Target Test Prep Representative
Status: Founder & CEO
Affiliations: Target Test Prep
Joined: 14 Oct 2015
Posts: 9416
Location: United States (CA)

Re: Five machines at a certain factory operate at the same constant rate
[#permalink]
Show Tags
22 May 2018, 16:42
nalinnair wrote: Five machines at a certain factory operate at the same constant rate. If four of these machines, operating simultaneously, take 30 hours to fill a certain production order, how many fewer hours does it take all five machines, operating simultaneously, to fill the same production order?
(A) 3 (B) 5 (C) 6 (D) 16 (E) 24 The rate of 4 machines is 1/30. We can let the rate of 5 machines be n and create the equation: 4/(1/30) = 5/n 120 = 5/n 120n = 5 n = 5/120 = 1/24 So it will take 1/(1/24) = 24 hours for the 5 machines to fill the same order and thus it takes 6 fewer hours than if the order were filled by 4 machines. Answer: C
_________________
5star 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.



Manager
Joined: 20 Jul 2018
Posts: 87
GPA: 2.87

Re: Five machines at a certain factory operate at the same constant rate
[#permalink]
Show Tags
19 Aug 2018, 20:24
Rate if 4 machines 1/30 Rate of 1 machine = 1/(30*4) Rate of 5 machines = 1*5/(30*4) = 1/24 So 5 machines complete work in 24 hourse and take 6 fewer hours. Answer is C Posted from my mobile device
_________________
Hasnain Afzal
"When you wanna succeed as bad as you wanna breathe, then you will be successful." Eric Thomas



Director
Joined: 19 Oct 2013
Posts: 507
Location: Kuwait
GPA: 3.2
WE: Engineering (Real Estate)

Re: Five machines at a certain factory operate at the same constant rate
[#permalink]
Show Tags
19 Oct 2018, 04:17
nalinnair wrote: Five machines at a certain factory operate at the same constant rate. If four of these machines, operating simultaneously, take 30 hours to fill a certain production order, how many fewer hours does it take all five machines, operating simultaneously, to fill the same production order?
(A) 3 (B) 5 (C) 6 (D) 16 (E) 24 The question asks for the difference in hours 4 machines finish in 30 hours so 1 machine finishes in 120 hours. 5 machines will then finish in 120/5 = 24 hours. The difference in hours is 2430 = 6. Answer choice C



Manager
Joined: 01 Jan 2019
Posts: 106
Location: Canada
Concentration: Finance, Entrepreneurship
GPA: 3.24

Re: Five machines at a certain factory operate at the same constant rate
[#permalink]
Show Tags
20 Jun 2019, 03:33
Hi can someone tell me where did I go wrong.
If 4 machines require 30 hours? So 5 machines will be 30*5/4?
I don’t know where have I gone wrong
Posted from my mobile device



Intern
Joined: 14 Oct 2019
Posts: 5

Re: Five machines at a certain factory operate at the same constant rate
[#permalink]
Show Tags
04 Jan 2020, 05:29
nalinnair wrote: Five machines at a certain factory operate at the same constant rate. If four of these machines, operating simultaneously, take 30 hours to fill a certain production order, how many fewer hours does it take all five machines, operating simultaneously, to fill the same production order?
(A) 3 (B) 5 (C) 6 (D) 16 (E) 24 4 machines take > 30 hours 1 machine takes > 30*4 hours 5 machines take > 30*4/5 hours Difference = 30*4/530= 6 hours Answer (C) 6 hours



Intern
Joined: 06 Jul 2018
Posts: 8

Re: Five machines at a certain factory operate at the same constant rate
[#permalink]
Show Tags
06 Jan 2020, 09:13
If 4 machines take 30 hrs, 5 machines will take 30*4/5= 24 hrs
#fewer hours= 3024= 6 hrs



Director
Joined: 19 Oct 2013
Posts: 507
Location: Kuwait
GPA: 3.2
WE: Engineering (Real Estate)

Re: Five machines at a certain factory operate at the same constant rate
[#permalink]
Show Tags
06 Jan 2020, 21:49
Shef08 wrote: Hi can someone tell me where did I go wrong.
If 4 machines require 30 hours? So 5 machines will be 30*5/4?
I don’t know where have I gone wrong
Posted from my mobile device Even though this is a late reply, you need to look at it this way. 4 machines require 30 hours so that would mean 1 machine require 120 hours. (4 * 30 = 120) Now you need to find how many hours will it require 5 machines to do the same job. 120/5 = 24 In your calculation it should be (30 * 4)/5



Manager
Joined: 05 Oct 2019
Posts: 53
Location: Georgia
Concentration: Marketing, General Management
GPA: 2.88

Re: Five machines at a certain factory operate at the same constant rate
[#permalink]
Show Tags
22 Jan 2020, 05:07
4 machine 30 day > 1 machine 120 day(cause it takes 4 times many for 1 machine to fill the order) > 5 machine 24 day > 3024=6 day less




Re: Five machines at a certain factory operate at the same constant rate
[#permalink]
22 Jan 2020, 05:07






