Pipes A and B can fill a tank in one hour and two hours respectively while pipe C can empty the filled tank in one hour and fifteen minutes. A and C are turned on together at 9 a.m. after 2 hours, only A is closed and B is turned on. When will the tank be emptied?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is Option 3 i.e 12:20 p.m.
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Understanding |
Application |
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Let the total work = LCM of (1, 2, 5/4) = 10 units Efficiency of A = 10/1 = 10 units per hour Efficiency of B = 10/2 = 5 units per hour Efficiency of C = 105/4 = -8 units per hour |
Work done by A+C in 2 hours = (10 – 8) × 2 = 4 units The efficiency of B and C = -3 Therefore, time taken by B+C to empty the tank = 4/3 hours = 80 minutes Now the time = 11:00 + 1 hr 20 minutes = 12:20 p.m. |