5 km/h

5 km/h

Topic 1.1 Extended A - Problem solving strategies

10 km

Consider two trains approaching each other on the same track. When they are 10 km apart a fly, who can travel at 2 m/s leaves one train and flies to the other, continuing to go back and forth without resting until the trains collide. How far, in total, does the fly travel?

Since the trains are each moving at 5 km/h, they approach each other at 10 km/h.

Since they are 10 km apart when the fly begins, he has exactly 1 hour to fly.

That is to say, he has 60 minutes, or 3600 seconds to fly.

Since he is flying at 2 m/s, we can use the formula d = rt to get the total distance of 7200 m, or 7.2 km.