Question: Two pipes A and B can fill a tank in 12 hours and 18 hours respectively. If both pipes are opened together, how long will it take to fill the tank?
Options:
Correct Answer: 9 hours
Solution:
The combined rate is 1/12 + 1/18 = 5/36. Therefore, it will take 36/5 = 7.2 hours to fill the tank.