A cross-country skier leaves a camp to explore a wilderness area. Two hours later a friend leaves the camp in a snowmobile, travelling 4 mph faster than the skier, and meets the skier 1 h later. Find the rate of the snowmobile. Solution Let s = speed of the snowmobile: Let (s-4) = speed of the skier : We know that when the snowmobile overtakes the skier, they will have traveled the same distance. Make an equation from that fact; d = time * speed : Traveling time for the skier: 3 hrs Travel time for the snmob: 1 hr : skier dist = snmbl dist 3(s-4) = 1s 3s -12 = s 3s - s = +12 2s = 12 s = 12/2 s = 6 mph is the speed of the snmob.