Please solve this question
Chapter motion

Solution : 

Radius = 50 cm = 0.5 m
time = 4 min = 240 s

Average speed = total distance travelled/ total time taken
  $$\begin{gathered} Avg speed = \frac{2\pi r}{t} = 0.01 m/s \\ Avg velocity = displacement / total time taken = 0 \\ As initial and final points are same. \end{gathered}$$