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?
Dave thinks it is ten minutes. Because if you take 20 minutes of the motorcycle trip it would be save 10 minutes both ways.
ReplyDeleteI originally thought that the time would be that the plane was early. But then as I worked through this problem I realized that it wasn't as easy as it first appeared. The horse is going slower than the motorcyclist so their time is different. I am guessing that the 30 minutes it took the horse to travel that distance would take the motorcyclist about 10 minutes. So the distance from where they met to the airport is 10 minutes there and 10 minutes back. That is 20 minutes. So my guess is that the plane arrived 20 minutes early.
ReplyDeleteThe title of this chapter was, "Draw a Diagram."
ReplyDelete