Question

A non stop bus goes from one station to another station with a speed of 54 km /hr then it turn back to station A at the rate of 36 km/ hr . Calculate it's average velocity ?

Answer 1

since the actual distance does not matter, call it 1km
average speed is totaldistance/totaltime
time = distance/speed, so
outbound time: 1/54
return time: 1/36
total round trip distance: 2km

so, the average speed is
2/(1/54 + 1/36) = 43.2 km/hr

FYI: the average velocity is zero, since the final displacement is zero.