Answer
The average velocity is less than 4.00 m/s because the runner spends more time running at a slower velocity.
Work Step by Step
The average velocity is less than 4.00 m/s because the runner spends more time running at a slower velocity.
We can check this by calculating the average velocity.
$t_1 = \frac{120.0 ~m}{3.00 ~m/s} = 40.0~s$
$t_2 = \frac{120.0 ~m}{5.00 ~m/s} = 24.0~s$
The total time is 64.0 seconds and the total displacement is 240.0 meters.
$v_{ave} = \frac{240.0 ~m}{64.0 ~s} = 3.75 ~m/s$