Final answer:
The correct equation for determining acceleration from a velocity vs. time graph is c) a = Δv / t, where acceleration is the rate of change of velocity over time.
Step-by-step explanation:
The equation most likely used to determine the acceleration from a velocity vs. time graph is c) a = Δv / t, where 'a' represents acceleration, 'Δv' represents the change in velocity, and 't' represents the time taken for that change. This equation aligns with the concept that acceleration is the rate at which velocity changes over time. Moreover, the gradient (slope) of a velocity-time graph directly indicates the acceleration when the acceleration is constant.