Matthew walks up and down a hill which is three kilometres each way. His dog, being slower, walks at half the speed. When Matthew reaches the top of the hill, he turns around and walks down to meet his dog part way. Matthew continues walking to the bottom of the hill maintaining his speed. The dog follows him, also maintaining his speed. How far does the dog walk?
Answer
Four kilometres. When Matthew reaches the top of the hill, he will have walked three kilometres, and his dog will be half-way, or 1.5 kilometres. Matthew then turns around and walks back, but his dog continues walking up the hill until they meet. They will meet at the two-kilometre point. The dog will turn around at this point and follow Matthew down the hill completing a 4-kilometre walk.