Question

a train 400 m long is running at the speed of 40 km/hr. how long will it take to cross a bridge 800 m long

Answer 1

distance =1200m
speed =40×(5÷18)m/sec
time =1200÷[(20×5)÷9]
=(1200×9)÷(20×5)
=108sec

Answer 2

Distance =800+400=1200m=1.2km
Train speed =40km/hr
Time = distance/speed
=1.2/40
=3/100
=.03hour
=1.8 min