Total distance covered:
d=2×10 km
d=20000 m
Time taken:
t=30 min
t=30×60 s=1800 s
Average speed is given by:
<v>=dt
<v>=20000 m1800 s
<v>=11.11 m/s
Since the car returns to the initial position, displacement (s) is 0.
Average velocity is given by:
vavg=st=0