Two trains each 350m long are moving in opposite directions.  They cross each other in 30 seconds. If the speed of one train is 50 km/h, find the speed of the other train.

34 km/hr

Total distance covered while crossing = 350 + 350 = 700 m

Time taken = 30 sec

Relative speed (S₁ + S₂) = \(\frac{Total\;Distance}{time}\) = \(\frac{700}{30}\) = \(\frac{70}{3}\) m/sec

                                     = \(\frac{70}{3}\) × \(\frac{18}{5}\) km/hr = 84 km/hr

Speed of one train = 50 km/hr (given)

Speed of other train = 84 - 50 = 34 km/hr