Question: A tank is filled by two pipes A and B in 12 hours and 16 hours respectively. If pipe A is opened for 4 hours and then pipe B is opened, how long will it take to fill the tank?
Options:
Correct Answer: 10 hours
Solution:
In 4 hours, A fills 1/3 of the tank. The remaining 2/3 can be filled by A and B together in 4 hours.