A motorcyclist was sent by the post office to meet a plane at the airport. The plane landed ahead of schedule, and its mail was taken toward the post office by horse. After half an hour, the horseman met the motorcyclist on the road and gave him the mail. The motorcyclist returned to the post office 20 minutes before he was expected. How many minutes early did the plane land?
Adopted from The Moscow Puzzles by Boris Kordemsky, taken from Crossing the River with Dogs.
The high school math teacher and I got into lengthy discussion/friendly argument over the answer to this question. I believe the answer to be 40 minutes and he insists it is 20 minutes. Who is correct and can you prove it? Or are both of us wrong?
