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Joined: 05 Sep 2016
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Re: Six machines, each working at the same constant rate [#permalink]
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04 Dec 2016, 02:34
if 6 machines do the job in 12 hours, then the ratio is 6:12. if we want to do the same job in 8 hours, then 12 need to be multiplied by 2/3, 12 * 2/3 = 8. Thus, since work and time are reciprocal, 6 machines have to be multiplied by 3/2, then 6 * 3/2 = 9. The answer is 9  6 = 3 additional machines.



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Re: Six machines, each working at the same constant rate [#permalink]
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20 Jan 2017, 02:06
A simple way to solve this problem is to form an equation based on inverse proportion : If 6 machines take 12 days to complete the job, logic says that more machines will be needed to do the same job in less no. of days (here 8 days). Let x be the additional machines needed to complete the job in 8 days. Hence, our equation will be: 6/ (6+x) = 8/12 Solve it for x to get 3 as the answer



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Re: Six machines, each working at the same constant rate [#permalink]
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20 Feb 2017, 17:35
Six machines to complete a job in 12 days means that every day each machine completes 1/72 of the job. So to complete a job in 8 days it would take 9 machines since 9 machines complete 9/72 of the job a day. Multiplied by 8 it will take those 9 machines 8 days to complete 72/72 percent of the job which is 100%.



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Re: Six machines, each working at the same constant rate [#permalink]
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28 Mar 2017, 11:00
speed time work 6 machines 6x 12 1 ? ? 8 1
As we know that machiens do the same work, we can say x=1, then they do 72, 72/8=9, 96=3 answer is 3



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Six machines, each working at the same constant rate [#permalink]
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22 Apr 2017, 15:47
srkaleem wrote: Six machines, each working at the same constant rate, together can complete a job in 12 days. How many additional machines, each working at the same constant rate, will be needed to complete the job in 8 days?
A. 2 B. 3 C. 4 D. 6 E. 8 Solution : 1. 1/12 = 6 X \(\frac{1}{X}\), thus we get X = 72. 2. \(\frac{6}{X}\) + ( y X \(\frac{1}{X}\) ) = 1/8, plugging X value = 72; thus we get y = 6 3. Difference between 2 value is the answer, thus = 3.
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Re: Six machines, each working at the same constant rate [#permalink]
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07 Apr 2018, 10:40
Hi All, We're told that 6 machines, working at the same constant rate, can finish a job in 12 days. We're asked for the number of EXTRA machines will you need to finish the job in 8 days? This type of question is easiest to solve if you convert the info into "work units" Here, we start with 6 machines working for 12 days. This equals (6)(12) = 72 machinedays of work to finish the job. If we wanted to finish the job in 8 days, it would still take 72 machinedays of work, so we'd need 72/8 = 9 machines. We already have 6 machines, so we need 3 MORE machines to get the job done in 8 days. Final Answer: GMAT assassins aren't born, they're made, Rich
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Joined: 14 Feb 2016
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Re: Six machines, each working at the same constant rate [#permalink]
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18 Apr 2018, 07:04
1) Find the total ‘days of work’ with 6 machines: 12*6 = 72. 2) Find the total amount of machines required 72 days of work, in 8 days. 72/8. 3) We find that 9 machines are required for 72 days of work. 4) This means we need 3 additional machines. Answer choice is B.



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Joined: 01 Apr 2018
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Re: Six machines, each working at the same constant rate [#permalink]
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18 Apr 2018, 07:12
srkaleem wrote: Six machines, each working at the same constant rate, together can complete a job in 12 days. How many additional machines, each working at the same constant rate, will be needed to complete the job in 8 days?
A. 2 B. 3 C. 4 D. 6 E. 8 Total work done = 12*6=72 unit Same work to be done by let n machine in 8 days : 8*n=72 or n=9 machine Hence extra machine require =96=3 nos Sent from my iPhone using GMAT Club Forum mobile app




Re: Six machines, each working at the same constant rate
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