A goods train 110m long is running with the speed of 30 km/hr. in what time will it pass a boy who is running at 3.5 km/hr in the direction opposite to that in which the train is going. A) 9 sec B) 10sec C) 12sec D) 13sec
ANSWER : C
Explanation:
Length of the train = 110 m
Speed of the train = 30 km/hr
Speed of the boy = 3.5 km/hr
Speed of the train relative to man = (30 + 3.5) km/hr
= 33.5 km/hr
Convert km/hr into m/s
33.5 km/hr = (33.5 * 5 /18) m/s
= 167.5 / 18
= 9.30 m/s
Time taken by the train to cross the man = time taken by it to cover 110 m at 9.30 m/s
= 110 / 9.30
= 11.8 seconds
= 12 sec(approx.).