Question: If a pipe can fill a tank in 9 hours and another pipe can fill it in 6 hours, how long will it take to fill the tank if both pipes are opened together?
Options:
Correct Answer: 4.5 hours
Solution:
The combined rate is 1/9 + 1/6 = 5/18. Therefore, it will take 18/5 = 3.6 hours to fill the tank.