Question

What is the physical quantity of the rate of change of displacement?

Answer 1

Rate of change of displacement is velocity.
Rate of change of distance is speed.
Here, the answer is displacement.

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Answer 2

Velocity is the physical vector quantity which is the rate of change of displacement which determines the direction as well as magnitude.
its formula is 
Velocity = Displacement/Time
and  in calculus terms  the formula is 
v=dx/dt
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