Mr. Martin and his son, Luke, decide to walk a 12 kilometer trail. Mr. Martin takes a 1-hour head start and walks at a pace of 3 km/hr. Explain how fast Luke should walk to reach the end of the trail in 3 hours, the same time as Mr. Martin.

Answer:

Mr. Martin will take 4 hours to walk the trail because 12 km divided by 3 km/hr equals 4 hours. Since Luke starts one hour later but wants to finish at the same time, he only has 3 hours to complete the 12 km trail. Using the equation 12 = r * 3 (or 12 = 3x), we find that Luke should walk at a speed of 4 km/hr.