Question

Matthew walks up and down a hill which is three kilometers 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 1

The total distance of dog + Matthew when they meet for the second time is 6 km.
Matthew will have run 4 km, the dog 2 km.
The dog has to walk all of that back to the base of the hill, so 4 km in total.
(The dog will have run 3 km by the time Matthew is back at the base of the hill.)