You need to fly once around the world. You have 3 seaplanes and lots of fuel, but a full tank lasts only halfway around the world. You can land and take off anywhere, transferring fuel as needed. Can you get around the world, ending up with all planes safe at the start?
Pierce, Rod. (13 Mar 2018). "Seaplane Puzzle". Math Is Fun. Retrieved 1 Sep 2021 from http://www.mathsisfun.com/puzzles/seaplane.html
Check your answer against the solution here!