Answer
61 km/hour. 0 km/hour.
Work Step by Step
The total distance is 500 km. The displacement is zero; the endpoint is the same as the beginning point.
Average speed: use distance traveled and the total time.
Calculate the time in the first leg by dividing the distance by the constant speed.
t1 = (250 km)(95 km/h) = 2.632 hr. Keep a few extra significant figures for now.
Do the same for the return trip.
t2 = (250 km)(55 km/h) = 4.545 hr.
The total time, including lunch, is 8.177 hr.
$$\frac{500 km}{8.177 h} = 61 km/h$$
The displacement is zero so the average velocity is zero.
