Posted by Capreeca on .
A marathon runner runs at a steady rate of 15 km/h. When the runner is 7.5 km from the finish, a bird begins flying from the runner to the finish at 30 km/h. When the bird reaches the finish line it turns around and flies back to the runner, and then turns around again, repeating the back and forth trips until the runner reaches the finish line. How many kilometers does the bird travel?

Physics 
bobpursley,
How long does the bird fly in the air, or how long does the runner run? ans: t=distance/velocity=7.5km/15km/hr= 30 min
how far does the bird fly? velocity*time=30km/hr*1/2hr= 15km