Quantity I : Relative speed of the trains = (75 + 69) km/hr = 144 km/hr = 144 × `5/18` m/sec = 40 m/sec Time taken by the trains to cross each other = Time taken to cover (250 + 150) m at 40 m/sec = (400/40) sec = 10 sec Quantity II : Time taken to cover 300 km = (300/75) h = 4h Number of stoppages = 300/100 - 1 = 2 Total time to stoppages = (5 × 2) min = 10 min Hence, total time taken = 4 hrs 10 min
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