Question

Two trains 150 kilometer apart travel towards each other on parallel tracks, each moving at 25 kilometer per hour. A bird flies back and forth between the two trains at 50 kilometer per hour, until the train passes each other how far does the bird fly?

Answer 1

the trains are closing at 50 kph (25 + 25)

they start 150 km apart, so it takes them 3 hr to meet (and pass)

the bird flies for 3 hr at 50 kph, so it flies 150 km