Answer
a) 4.4m/s
b) -0.73 m/s
Work Step by Step
a) Running east: t=$200m\div5.0m/s $= 40.0s
Running west: t= $280m\div4.0/m/s$ = 70.0s
Average speed for total trip= $\frac{200m+280m}{40.0s+70.0s}$=4.4m/s
b) Average velocity= $v_{av-x}$=$\frac{\Delta x}{\Delta t}$=$\frac{200m-280m}{40.0s+70.0s}$=-0.73 m/s
