Two train 110 m and 140 m long are running in same direction on a parallel track at the speed of 70 km/hr and 50 km/hr respectively. How long the faster train will take to cross the slower train?

45 sec.

To cross the train, total distance to be traveled = Sum of length of trains

Distance = 110 + 140 = 250 m

Relative speed in same direction = S₁ - S₂ = 70 - 50 = 20 km/hr = 20 × \(\frac{5}{18}\) m/sec

⇒ Time to cross the slower train = \(\frac{Distance}{Relative\;Speed}\)

                                               = \(\frac{250\;×\;18}{20\;×\;5}\)

                                               = 45 Sec.