A boy on a train notices that he can count 31 telephone posts in 60 seconds. The distance between the two posts is 60 meters. Calculate the speed of the train?

Show answer & explanation

Answer: (B) 108 km/hr

Explanation

Counting 31 posts means passing 30 gaps between them: 30 × 60 = 1,800 m in 60 seconds, i.e. 30 m/s. Converting: 30 × 18/5 = 108 km/h.