A train crosses a man running in the direction of train with the speed of 12 km/hr in 10 seconds whereas when a person runs in the opposite direction with the speed of 8 km/hr the train crosses in 5 seconds . Find the speed of train .
Answer & explanation
Correct answer: option 3
Distance = Speed × Time
Let speed of train = a km/hr
When train and the man with speed 12 km/hr move in same direction
Relative speed = ( a - 12 ) km/hr
Distance = ( a - 12 ) × 10 ---------- ( 1 )
When train and the man with speed 8 km/hr move in opposite direction
Relative speed = ( a + 8 ) km/hr
Distance = ( a + 8 ) × 5 ------------- ( 2 )
Distance is same . so put equation 1 and 2 equal
( a - 12 ) × 10 = ( a + 8 ) × 5
2a - 24 = a + 8
a = 32 km/hr