일반물리학 1 — Motion Along a Straight Line: Problem 3

3 Rachel walks on a straight road from her home to a gymnasium 2.80 km away with a speed of 6.00 km/h. As soon as she reaches the gymnasium, she immediately turns and walks back home with a speed of 7.70 km/h as she finds the gymnasium closed. What are the (a) magnitude of average velocity and (b) average speed of Rachel over the interval of time 0.00–35.0 min?