Question

A train travels the first 30km of 120km track with a uniform speed of 30km/h.What should be the speed of the train to cover the remaining distance of the track so that its average speed is 60km/h for the entire trip?

Answer 1

Let the speed of the train after 30 kms be S2

Therefore, S1 = 30km/h, S2 = ?

Average speed = S1+S2/2

30 + S2
60 km/h =------------
2

120 = 30 + S2
S2 = 90 km/h