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Three pipes A, B and C are attached to a tank. A can empty the tank in 12 hours, B can empty it in 15 hours and C can fill it in 3 hours. The tank was 1/3rd full at 10’o clock and pipe A and B were open at the same time. At 12’o clock someone opened C and turned off B. When will the tank fill?1. 4 hours2. 58/15 hours3. 59/15 hours4. 57/15 hours5. 11/3 hours |
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Answer» Correct Answer - Option 2 : 58/15 hours Given: A and B can empty the tank in 12 and 15 hours respectively whereas C fills it in 3 hours. A and B ran for 2 hours and then A and C ran for some time. Formula used: Total volume = resultant flow × time Calculation: Let us assume the volume of the tank = LCM of (12, 15, 3) = 60 lit A empties = 60/12 = 5 lit/hr B empties = 60/15 = 4 lit/hr C fills = 60/3 = 20 lit/hr The tank was 1/3rd filled initially. Initial volume = 1/3 × 60 = 20 lit A and B empties = (5 + 4) × 2 = 18 lit Volume of water required to fill the tank = (60 – 20 + 18) = 58 lit Resultant flow when A and C are open = (20 - 5) = 15 lit Time required = 58/15 hour |
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