Explanation:
Instantaneous velocity is specific rate of the change of the position or the displacement with respect to the time at a particular single point (x,t)
[tex]v(t)=\frac{d}{dt}x(t)[/tex]
Average velocity is average rate of the change of the position or the displacement with respect to the time over an particular interval.
[tex]{v}=\frac {\Delta x}{\Delta t}=\frac{{x}_{\text{f}}-{x}_{\text{i}}}{{t}_{\text{f}}-{t}_{\text{i}}}[/tex]