Question Statement :

A tank has two inlet pipes which can fill the empty tank in 12 hours and 15 hours working aloneand one outlet pipe which can empty the full tank in 8 hours working alone. The inlet pipes arekept open for all the time but the outlet pipe was opened after 2 hours for one hour and thenagain closed for 2 hours then once again opened for one hour. This pattern of outlet pipecontinued till the tank got completely filled. In how many hours the tank has been filled, workingon the given pattern?