Pipe A can fill a tank in 6 hours, and Pipe B can fill the same tank in 3 hours. If both pipes are opened simultaneously, how many hours will it take to fill the tank?

✓ Correct Answer: Option A

Pipe A fills 1/6 of the tank per hour, and Pipe B fills 1/3 of the tank per hour. Together, their combined rate is 1/6 + 1/3 = 1/6 + 2/6 = 3/6 = 1/2 of the tank per hour. Therefore, it will take 1 / (1/2) = 2 hours to fill the tank.