Answer:
The rate of the runner is 3.5 meters per second.
Step-by-step explanation:
To get this answer in meters per second, we first have to convert each of the terms into either meters or seconds. We can do that by multiplying by unit rates.
21 km * 1000 = 21,000 meters
1 hour * 3600 = 3,600 seconds
40 minutes * 60 = 2,400 seconds
Now we divide the meters by the total number of seconds to get the rate.
21,000 meters / (3,600 + 2,400) secs
21,000 meters / 6,000 secs
3.5 meters per second.
