Numerical answer
Pipes A and B can fill an empty tank in 10 minutes and 18 minutes respectively, while pipe C can empty the full tank in 9 minutes. All three pipes are opened together on the empty tank, and C is closed after 5 minutes. In how many minutes from the start will the tank be full?
Show answer and solution
Answer: 10
Take tank capacity = 90 units (LCM of 10, 18, 9). Rates: A = +9, B = +5, C = −10 units/min.
First 5 minutes (all open): net 9 + 5 − 10 = 4 units/min → 20 units filled.
Remaining 70 units with A and B: 14 units/min → 5 more minutes.
Total = 5 + 5 = 10 minutes.
First 5 minutes (all open): net 9 + 5 − 10 = 4 units/min → 20 units filled.
Remaining 70 units with A and B: 14 units/min → 5 more minutes.
Total = 5 + 5 = 10 minutes.
Saved on this device. Sign in or create a free account to keep it on every device.