Walk the Dog.

RAY: Here's the answer. When the man has reached the top of the hill, he's walked three kilometers because the whole trip is six. But the dog has walked only a kilometer and a half.

TOM: Correct.

RAY: Now the man at that point starts walking back down the hill. But the dog doesn't know that and continues to walk up the hill.

TOM: Right.

RAY: At some point they're going to meet, and the question is, where do they meet? Because the owner walks twice as fast as the dog and they start 1.5 kilometers apart, right?

TOM: Right.

RAY: The man will have walked one kilometer down the hill, while the dog is walking up the hill and goes a half a kilometer. So the dog will have walked a kilometer and a half, plus a half a kilometer. They'll meet at the two kilometer mark, two kilometers from the house.

TOM: Uh-huh.

RAY: So when the dog turns around and heads for home he will have walked two kilometers up the hill and two kilometers down the hill.

TOM: Excellent.

RAY: Do we have a winner?

TOM: The winner this week is Linda Soyarz from Aiken, South Carolina, and for having her answer selected at random from among both of the correct answers that we got, I mean the hundreds of correct answers...

RAY: Thousands.

TOM: Linda is going to get a 26-dollar gift certificate to the Shameless Commerce Division at cartalk.com, where she can get a copy of our CD of great stories that we have told on the air called, "Once Upon a Car Fire." Congratulations Linda.

RAY: As for the dog, it was a Portuguese Water Dog. Had the man hit the pool for his morning exercise, we'd be telling a very different story.

[ Car Talk Puzzler ]