Question

Two pipes A and B can fill a tank in 36 minutes and 24 minutes respectively. Both pipes are opened together. But 12 minutes before the tank will fill, pipe B is closed. In how much time will the tank be totally filled ?

• A. 18 minutes 36 seconds
• B. 22 minutes 26 seconds
• C. 21 minutes 36 seconds
• D. 24 minutes 12 seconds

Answer 1

Answer:

C. 21 minutes 36 seconds

Total quantity = lcm[36, 24] = 72 Efficieny of A = 72/36 = 2 Efficieny of B = 72/24 = 3 12 minutes before the tank is full pipe B is closed, So A alone is worked for 12 minutes Tank filled in 12 minutes = 12 × 2 = 24 Remanining = 72 - 24 = 48 Work done by A + Work done by B = 48/5 = 9⅗ Total time = 12 + 9⅗ = 21⅗ = 21 minutes 3/5 × 60 seconds = 21 minutes 36 seconds