Walk the Dog.
RAY: I've received this puzzler over the years from a whole bunch of different people. And I got this most recent one from the same guy who sent in the cow and kine puzzler. It made me decide to use it. I figure if he's going to be in trouble, I might as well get him in more trouble. Here it is - I had to post-obfuscate, but it's basically the same.
A man who owned a dog lived at the bottom of the hill. It was their habit every morning to walk the three kilometers to the top of the hill and then back for exercise, for both the dog and the owner. Well, time has gone on and the dog has gotten older. The man still walks to the top of the hill every morning, but the elderly dog can't quite keep up with him.
So now what they do is this: The man starts out at his usual steady pace and the dog follows but at half the man's speed. So when the man reaches the top he turns around and starts back down, maintaining the same steady pace. Before long he meets the dog coming up the hill and at this point the dog turns around and starts back down again.
And I'll add an additional wrinkle, because they're going down the hill, now the man and the dog walk at the same speed down the hill because gravity's helping the dog down the hill. And they get home together.
Two part question: What kind of a dog is it? And two, how far does the dog walk?
Think you know? Drop Ray a note!
[ Car Talk Puzzler ]