Question

A train covered the distance of 400 km between A and B at a certain speed. On the way back it covered 2/5 of the distance at that same speed and then it decreased its speed by 20 km/hour. Find the speed of the train at the end of its journey from B back to A, if the entire trip took 11 hours.

Answer 1

if the initial speed is x, then since time=distance/speed,

400/s + 160/s + 240/(s-20) = 11

Answer 2

400/x + 160/x + 240/(x-20) = 11
x = 80, 140/11
80 - 20 = 60

60 km/hr