RRB Group D 13-Dec-2018 Shift 2 Solved Paper

There are two inlet pipes, Pipe A and Pipe B, filling an empty tank. A lone, Pipe A can fill an empty tank to 1/2 of tank’s capacity in 5 hours.
A lone, Pipe B can fill an empty tank to 3/5 of tank’s capacity in 9 hours. Both the pipes pumping at their respective constant rates. How many hours will it take both pipes, pumping simultaneously at their respective constant rates, to fill the empty tank to its capacity?