How do I find the instantaneous velocity of an object?

Question

vincent-lyon.fr · Answer

Derive its displacement with respect to t.

anonymous · Answer

I'm doing an even more basic question than that, I am given a line graph with different values for position vs time. I am asked to find the instantaneous velocity at t=4 seconds.
Does this mean I should start by finding the average velocity from 0 to 4?

vincent-lyon.fr · Answer

Velocity is the time-derivative of position. That means the gradient of the curve at t=4s will give you the value of the instantaneous velocity.

anonymous · Answer

the velocity of an object at any given instant (especially that of an accelerating object) and the change actually is the derivative with respect to some independent vaiable.
$$\lim_{t \rightarrow 0}\frac{ dX }{ dt }$$