400 metre long train ‘A’ is running with a speed of 61.2 km/hr. Train ‘B’ which is 442 metre long is running with a speed of 90 km/h in opposite direction of train ‘A’. For how much time, the smaller train is completely obscured by the larger train when they cross each other?
Length of smaller train = 400 metre Speed of smaller train = 61.2 × (5/18) = 17 m/s Length of bigger train = 442 metres Speed of bigger train = 90 × (5/18) = 25 m/s Since, the smaller train is completely obscured by larger train, therefore, extra length of larger train = 442 – 400 = 42 metres Relative speed of trains ‘A’ and ‘B ‘= 17 + 25 = 42 m/s (Since, the trains are running in opposite direction) Required time = 42/42 = 1 second
