The eagle is at Ferny Bank station and, 100 miles away, the train is at Waterfall station.
They both leave at the same time and (don't ask me why!) the eagle flies towards the train at 80 mph.
The train travels at 40mph.
When the eagle reaches the train, she immediately flies back to Ferny Bank. She repeats this until both are at Ferny Bank.

How far does the eagle fly altogether?

My solution.

Since the eagle flies at
twice the speed of the train,
she will fly twice as far.

So the answer is simply 200 miles!