Answer
60 km
Work Step by Step
Since the trains are going the same speed, the train will collide at the midpoint of 60 km, which means one train will travel a total of 30 km. The bird is going double the speed of the trains. In the time it takes for the train to go 30 km (where they will collide) the bird will have gone 60 km because the bird is twice as fast as the trains.