Question

a person standing on a railway platform noticed that a train took 21 secs to completely pass through the platform which was 84m long and it took 9 seconds in passing him. find the speed of the train in km/hr

Answer 1

The time needed to pass through the man = 9s

⇒ That is the time needed for the train to clear its own length

Find the speed of the train:

Time needed for the head of the train to clear the platform = 21 - 9 = 12sec

Distance of the platform = 84 m

12 sec = 84 m

Find 1 sec:

1 sec = 84 ÷ 12 = 7m

Find 1 min:

1 min = 7 x 60 = 420 m

Find 1 hour:

1 hour = 420 x 60 = 25200 m

Find in km:

1 hour = 420 x 60 = 25.2 km

Answer: Speed of the train = 25.2km/h