➡Complete solution :-
➡Let the distance between two stations = d km
➡After, the journey the train returns to the first station.
➡Total distance travelled = 2d
Net displacement of the train = 0
➡So, the train time taken to travel one station to another station = t1= d/40hrs
Time take by the train when come back , t2= d/60hrs
Therfore, total time taken by the train to round the trip is
t = t1+t2= d/40 + d/60 = d/24hrs
➡Avg . Speed = 2d/ d/24 = 48 km/ h
➡Avg. Velocity = 0/ d/24 = 0 km/ h