Xiaoming needs to walk 5 kilometers from the library to his home. It took him 40 minutes. How many kilometers does he walk per hour on average? The idea to solve this problem should be that distance ÷ time equals speed, so 5000÷40 equals 125m, which is the average driving speed per minute. Converted into hours, it needs ×60, that is, 125×60 equals 7500m. The correct answer is to walk 7500 meters per hour, mainly to test students' transformation of time. From average speed per minute to speed per hour.