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 .

32 km/hr

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