Answer:
66.7 mph
Explanation:
Average speed = total distance / total time
We know the total distance is 200 miles. We need to find the total time.
During the first trip:
t = 100 mi / 100 mph
t = 1 h
During the second trip:
t = 100 mi / 50 mph
t = 2 h
So the average speed is:
s = 200 mi / 3 h
s = 66.7 mph
Round as needed.