Answer:
6.25 m/s
Explanation:
Given parameters
Initial mark = 65
Final mark  = 15
time taken = 8s
Unknown:
Velocity of the runner  = ?
Solution:
Velocity is the displacement divided by time;
    Velocity  = [tex]\frac{displacement}{time}[/tex] Â
Displacement  = Initial mark - final mark  = 65 - 15 = 50m
Now, insert the parameters and solve;
    Velocity  = [tex]\frac{50}{8}[/tex]  = 6.25m/s