Given: Train passes a man in 10 seconds Thus it travels its own length in 10s Length of platform = 100 m Time to cross the platform = 14 seconds i.e it crosses its length and length of platform in 14 sec Formula used: Distance = speed × time Calculation: Length of train = speed × 10 ----(i) ∴ length of train + 100 = speed × 14 ----(ii) Subtracting both equations, we get 100 = speed × 14 ⇒ speed = 25 m/s ∴ Speed = 25 × 18/5 = 90 km/hr