Two pipes A and B can separately fill a tank in 2 hours and 3 hours respectively. If both the pipes are opened simultaneously in the empty tank, then the tank will be filled in:
[A]1 hour 12 minutes
[B]1 hour 15 minutes
[C]1 hour 20 minutes
[D]2 hours 30 minutes

1 hour 12 minutes
Part of the tank filled by pipe A and B in 1 hour
= \frac{1}{2}+\frac{1}{3}=\frac{3+2}{6} = \frac{5}{6}\ parts
∴ Required Time = \frac{6}{5}\ hours
= 1\ hour\ \frac{1}{5}\times 60 = 12\ minutes.
Hence option [A] is correct answer.