A pipe X can fill a tank in 20 hr. and capacity of tank is 200 gallon. Tank has one more pipe Y and it is an outlet pipe. It is twice efficient than X. Time taken by Y to empty 3 / 4 part of the tank is _________?
1
6 hours 20 min.
2
7 hours 30 min.
3
5 hours 40 min.
4
6 hours 45 min.
5
None of these