Pipes & Cisterns · Question 29 · Hard
Pipes & Cisterns question 29
Pipes A, B and C can fill a tank in 10, 15 and 30 hours respectively. A is opened on the empty tank, B is opened 1 hour later and C another hour after that. How long after A was opened will the tank be full?
- 5 hours
- 5 hours 40 minutes
- 5 hours 20 minutes
- 6 hours
Answer and explanation
Answer: B. 5 hours 40 minutes
Explanation: If the tank is full at time t (t ≥ 2), then t/10 + (t − 1)/15 + (t − 2)/30 = 1. Multiplying by 30: 3t + 2t − 2 + t − 2 = 30, so 6t = 34 and t = 17/3 hours = 5 hours 40 minutes.
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