Pipes A and B can fill a tank in 6 hours and 8 hours respectively, and pipe C can empty the full tank in 24 hours. If all three pipes are opened together on an empty tank, how long will it take to fill?

💡 Solution & Explanation

Take the tank as 24 units (the LCM of 6, 8 and 24). Per hour, A fills 4 units, B fills 3 units and C empties 1 unit. Net filling = 4 + 3 − 1 = 6 units per hour. Time = 24 ÷ 6 = 4 hours. Adding C as a filling pipe would give 3 hours, which is too fast.