Question

Two trains 140 m and 160 m long run at the speed of 60 km/hr and 40 km/hr respectively in opposite directions on parallel tracks. The time (in seconds) which they take to cross each other, is:?

Answer 1

relative speed
=( 60 + 40) km/hr
= 100 km/hr

distance
= 140 + 160
= 200 m
= 200/1000 km
= 1/5 km

time
= distance /speed
=( 1/5/ 100 ) hr
= 1/500 hrs
= (1/500 x 60 x 60 )sec
= 36/5 sec
= 7.2 sec