Two trains, each having a speed of 35 km/h, are headed at each other on the same straight track. A bird that can fly 70 km/h flies off the front of one train when they are 70 km apart and heads directly for the other train. On reaching the other train it flies directly back to the first train, and so forth. (We have no idea why a bird would behave in this way.) What is the total distance the bird travels?

Explanation:

The two train are traveling at 35km/hr

A bird starts from one of the train and travel at 70km/hr

The distance between the two train is 70km.

The bird is going to and fro, so since we know the speed of the bird, we only need to know the time the two train will collide

So let calculate the time the two train will meet

Since each train is traveling at 35km/hr

The train will collide at mid point of their distance apart, so let know the time each of the train will get their

Time to each train will get to 35km

Velocity =distance/time

Time =distance/velocity

Time=35/35

Time = 1hour

Therefore, the bird will fly for 1hr before been crushed down by the train

Since the bird is traveling at 70km/hr

Therefore total distance the bird will travel

Distance = velocity × time

Distance = 70 ×1

Distance =70km

So the bird will travel for 70km.