Let the speed of the train during returning journey be x km/h
Speed during onward journey = x + 25x/100 = 5x/4 km/h.
Distance coverd in onward journey = 800 / 2 = 400 km
Total time taken = Covered distance / Speed
Time taken by train in onward journey = 400/(5x/4)
and time taken in returning journey = 400/x
Thus, 400/(5x/4) + 400/x = 16
⇒ 320/x + 400/x = 16
⇒ 16x = 720
∴ x = 45 km/h
Speed of the train in the onward journey = 5 x 45/4 = 56.25 km/h