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Five machines at a certain factory operate at the same constant rate
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24 May 2016, 22:19
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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
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Re: Five machines at a certain factory operate at the same constant rate
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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




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Re: Five machines at a certain factory operate at the same constant rate
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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
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Re: Five machines at a certain factory operate at the same constant rate
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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
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Re: Five machines at a certain factory operate at the same constant rate
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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
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Re: Five machines at a certain factory operate at the same constant rate
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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.



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Five machines at a certain factory operate at the same constant rate
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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.
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Re: Five machines at a certain factory operate at the same constant rate
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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.
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Re: Five machines at a certain factory operate at the same constant rate
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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
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Re: Five machines at a certain factory operate at the same constant rate
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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
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Re: Five machines at a certain factory operate at the same constant rate
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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




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