Consider three identical airplanes starting at the same airport. Each plane has a fuel tank that holds just enough fuel to allow the plane to travel half the distance around the world. These airplanes possess the special ability to transfer fuel between their tanks in mid-flight.
What are the maximum around the world trips that airplane1 can make?
Solution: 1 Trip
Planes 1 and 2 take off eastbound, and travel a quarter of the way around the world. At this point, both their tanks are half empty, so 2 transfers all of its fuel to plane 1 and lands. Now plane 1 has a full tank.Once plane 1 is halfway around the world, plane 3 takes off westbound and meets plane 1 when plane 1 is three quarters of the way around the world. At this point, plane 1’s tank is empty and plane 3’s is half empty. Plane 3 then transfers all its fuel to plane 1, who is thus able to finish the last quarter of the journey.