Two trains 75 km apart approach each other on parallel tracks, each moving at 15 km/h. A bird flies back and forth between the trains at 20 km/h until the trains pass each other. How far does the bird fly?

Question

Two trains 75 km apart approach each other on parallel tracks, each moving at 15 km/h. A      bird flies back and forth between the trains at 20 km/h until the trains pass each other. How        far does the bird fly?

anonymous · Answer

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anonymous · Answer

Find the time it takes for the trains to meet: 
t =  distance/(2 x 15)

The bird flies for this time at 20 km/h so files d = 20 t.

Much easier than trying to get the little back-and-forth flight paths.