The main formula used in work-rate, distance-speed problems is:
Work=Rate*Time, or Distance=Speed*Time.
Thus, the time is: [tex]speed= \frac{distance}{time} [/tex].
In our problem, the total distance is 3 km + 3 km = 6 km.
the total time is 20 min + 25 min = 45 min.
60 minutes are 1 hour, then
45 minutes are [tex] \frac{45min*1h}{60min}= 0.75h[/tex]
Thus, the average speed is : distance/time = 6 km/ 0.75 h = 8 km/h
Answer: 8 km/h
