Two trains 130 m and 140 m long are running on parallel tracks in the same direction with a speed of 68 km/hr and 50 km/hr. How long will it take to clear off each other from the moment they meet?
Solution: Â Â Â Â Â Â
Relative speed of trains = (68 – 50) km/hr
                = 18 km/hr
                = 18 × 5/18 m/sec
                = 5 m/sec
Time taken by the train to clear off each other = sum of length of trains/relative speed of trains
                                = (130 + 140)/5 sec
                                = 270/5 sec
                                = 54 sec
2. The two trains are running on parallel tracks in the same direction at 70 km/hr and 50 km/hr respectively. The faster train passes a man 27 second faster than the slower train. Find the length of the faster train.
Relative speed of the trains = (70 – 50) km/hr
                   = 20 km/hr
                   = 20 × 5/18 m/sec
                   = 50/9 m/sec
Length of the faster train = relative speed × time taken by train to pass
                   = 50/9 × 27 m
` Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
