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Working alone, pump A can empty a pool in 3 hours. Working a
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27 May 2014, 06:20
27 May 2014, 06:20
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Question Stats:
93% (00:37) correct
6% (01:24) wrong based on 30 sessions
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Working alone, pump A can empty a pool in 3 hours. Working alone, pump B can empty the same pool in 2 hours. Working together, how many minutes will it take pump A and pump B to empty the pool?
A. 72
B. 75
C. 84
D. 96
E. 108
Level: Medium.
A. 72
B. 75
C. 84
D. 96
E. 108
Level: Medium.
Re: Working alone, pump A can empty a pool in 3 hours. Working a
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14 Jul 2014, 03:38
14 Jul 2014, 03:38
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Re: Working alone, pump A can empty a pool in 3 hours. Working a
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23 Jun 2020, 10:45
23 Jun 2020, 10:45
1
Pump A takes 3 hours to empty the entire pool, thus in 1 hour it empties 1/3 of the pool
Pump B takes 2 hours to empty the entire pool, thus in 1 hour it empties 1/2 of the pool
If working together, in 1 hour 1/3 of the total pool's volume will be empties by pump A and 1/2 of the total pool volume will be emptied by pump B. If you add 1/2 and 1/3 you get 5/6 of the pool being emptied by two pumps working in 1 hour. Now you are just left with 1/6 of the pool to be emptied. Since it took two pumps 60 min to empty 5/6 of the pool, it will take them a fifth of the hour to empty the remaining 1/6th (which is 12 min: 60/5).
Thus total time needed is 1 hour and 12 min which equals to 72 min
Pump B takes 2 hours to empty the entire pool, thus in 1 hour it empties 1/2 of the pool
If working together, in 1 hour 1/3 of the total pool's volume will be empties by pump A and 1/2 of the total pool volume will be emptied by pump B. If you add 1/2 and 1/3 you get 5/6 of the pool being emptied by two pumps working in 1 hour. Now you are just left with 1/6 of the pool to be emptied. Since it took two pumps 60 min to empty 5/6 of the pool, it will take them a fifth of the hour to empty the remaining 1/6th (which is 12 min: 60/5).
Thus total time needed is 1 hour and 12 min which equals to 72 min
