A boy, a girl and a dog are standing together on a long, straight road. Simultaneously, they all start walking in the same direction: The boy at 4 mph, the girl at 3 mph, and the dog trots back and forth between them at 10 mph. Assume all reversals of direction instantaneous.

In one hour, where is the dog and in which direction is he facing?

(In reply to Question by Penny)

There can be no initial time for the dog to reverse its course, so the dog does not reverse its course. Hence the dog is 10 miles ahead of the starting point one hour after the start. The problem would make more sense if it were given that the dog first reverses its course at some definite time T and then goes back and forth after that.

Posted by Richard on 2004-01-24 20:43:45