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Five machines at a certain factory operate at the same constant rate

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Five machines at a certain factory operate at the same constant rate [#permalink]

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24 May 2016, 23:19
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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 [#permalink]

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25 May 2016, 01:19
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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

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Re: Five machines at a certain factory operate at the same constant rate [#permalink]

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25 May 2016, 07:34
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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 = $$30-24 = 6$$
C
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Re: Five machines at a certain factory operate at the same constant rate [#permalink]

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25 May 2016, 07:43
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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..

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Re: Five machines at a certain factory operate at the same constant rate [#permalink]

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25 May 2016, 08:40
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= 30-24= 6 hrs

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Joined: 08 Nov 2015
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Re: Five machines at a certain factory operate at the same constant rate [#permalink]

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08 Jan 2017, 00:50
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 30-24 = 6 hours.

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Re: Five machines at a certain factory operate at the same constant rate [#permalink]

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29 Jan 2018, 00:26
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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).

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Re: Five machines at a certain factory operate at the same constant rate   [#permalink] 29 Jan 2018, 00:26
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