450 metre long train ‘A’ is running with a speed of

Solution

Length of smaller train = 450 metre Speed of smaller train = 99 × (5/18) = 27.5 m/s Length of bigger train = 555 metres Speed of bigger train = 90 × (5/18) = 27.5 m/s Since, the smaller train is completely obscured by larger train, therefore, extra length of larger train = 555 – 450 = 105 metres Relative speed of trains ‘A’ and ‘B ‘= 27.5 + 25 = 52.5 m/s (Since, the trains are running in opposite direction) Required time = 105/52.5 = 2 second