how long has the hunting dog run?

Question

two hunters 100k apart walking towards each other at 5k/hr and 15k/hr speed respectively. one has a hunting dog running towards the other at 30k/hr speed. once the dog meets the other hunter it starts to run back. so on and so forth. the dog runs till the hunters meet. how long has the dog run?

Answer 1

Hmmm..one is walking 15 k/hr and the other 5 k/hr. They have a combined rate then of 20 k/hr and have to cover 100 km. Looks like they meet in 5 hours so the dog runs for 5 hours.