Question

Two pipes A and B can fill a tank in 10 and 15 minutes respectively. Both the pipes are opened together but 10 minutes before the tank is full pipe A is closed in how many minutes the tank will totally fill?

• A. 10 minutes
• B. 15 minutes
• C. 8 minutes
• D. 12 minutes

Answer 1

Answer:

D. 12 minutes

Total quantity = lcm[10, 15] = 30 Efficieny of A = 30/10 = 3 Efficieny of B = 30/15 = 2 10 minutes before the tank is full pipe A is closed, So B alone is worked for 10 minutes Tank filled in 10 minutes = 10 × 2 = 20 Remanining = 30 - 20 = 10 Work done by A + Work done by B = 10/5 = 2 Total time = 10 + 2 = 12