To find the average speed, you divide the total distance by the total time. The formula for average speed is

Average Speed = Total Distance over Total Time Total Distance Total Time

Let's look again at the sample problem from section one.

Pretend you went on a walk through your neighborhood. You walk 5 km to the neighborhood park, and it takes you 45 minutes. You stop and rest for 25 minutes at the park, and then you walk 5 km back home. It takes you 50 minutes to walk back home from the park.

First, determine what the total distance. What was the total distance? Interactive popup. Assistance may be required. The problem says you walked 5 km to the park and 5 km back home, so the total distance was 10 km.

Second, determine the total time. What was the total time? Interactive popup. Assistance may be required. It took 45 minutes to get to the park plus a 25 minute rest and the 50 minutes home. That is a total of 120 minutes or 2 hours.

Calculate the average speed. What is the average speed? Interactive popup. Assistance may be required. Average Speed = 10 km over 2 hours 10 km 2 hours
Average Speed = 5km over hour km hour

When you think about the units for speed, you probably think of miles per hour (miles/hr). In science, speed is expressed as kilometer/hour (km/hr) or as meters/second (m/s).