A train takes 11 sec and 10 sec to cross two men who are walking in same direction at the speed of 5 km/hr and 4 km/hr respectively. Find speed of the train .
Answer & explanation
Correct answer: option 4
Distance = Speed × Time
Let speed of train = a km/hr
When train and the man with speed 5 km/hr move in same direction
Relative speed = ( a - 5 ) km/hr
Distance = ( a - 5 ) × 10 ---------- ( 1 )
When train and the man with speed 4 km/hr move in opposite direction
Relative speed = ( a - 4 ) km/hr
Distance = ( a - 4 ) × 5 ------------- ( 2 )
Distance is same . so put equation 1 and 2 equal
( a - 5 ) × 11 = ( a - 4 ) × 10
11a - 55 = 10a - 40
a = 15 km/hr