Two friends plan to meet. They both own a bike and hops on to their respective bikes and kick start the journey together deciding to meet halfway. Each of them is riding at 6 MPH and their houses are 36 miles apart from each other. One of them has a dog who also begins running at that very instant. The dog keeps running back and forth at 18 MPH from one friend to another till they meet at the half way.

Can you calculate the distance that the dog has traveled in total?

54

This problem is much simple than it appears to be. Just see to the fact that it will take 3 hours for the friends to meet. How? Go figure out with Speed, Distance and Time relations. Now, he dog will be running for three hours in total at 18 MPH. Thus he will cover a total distance of 18 * 3 = 54 miles.