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22 Mar 2022, 07:45
Kudos
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Difficulty:
15%
(low)
Question Stats:
83% (02:04) correct
17%
(02:31)
wrong
based on 233
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If five machines working at the same rate can do \(\frac{3}{4}\) of a job in 30 minutes, how many minutes would it take two machines working at the same rate to do \(\frac{3}{5}\) of the job?
(A) 45
(B) 60
(C) 75
(D) 80
(E) 100
(A) 45
(B) 60
(C) 75
(D) 80
(E) 100
22 Mar 2022, 11:32
Kudos
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30 mins----3/4 th job by 5 m/c
1 min-----1/30*3/4= 1/40 th job by 5 m/c
1 min 1 m/c---1/40*1/5 = 1/200 th job
1 min 2 m/c ---1/200*2= 1/100 th job
2 m/c 3/5 th job----(3/5)/(1/100) = 3/5*100= 60 mins( Answer)
Posted from my mobile device
1 min-----1/30*3/4= 1/40 th job by 5 m/c
1 min 1 m/c---1/40*1/5 = 1/200 th job
1 min 2 m/c ---1/200*2= 1/100 th job
2 m/c 3/5 th job----(3/5)/(1/100) = 3/5*100= 60 mins( Answer)
Posted from my mobile device
22 Mar 2022, 11:56
Kudos
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If we simply reduced the number of machines from 5 to 2, the time would be multiplied by 5/2. If we also reduce the work from 3/4 of a job to 3/5 of a job, the time will be reduced by a factor of (3/5)/(3/4) = 4/5. So overall the time will be multiplied by (5/2)(4/5) = 4/2 = 2, and it will take 60 minutes.
