Kinematic Concepts - Mission KC7 Detailed Help

A ball falls from rest for 0.67 seconds, reaching a final speed of 6.57 m/s (downward or -) just prior to hitting the ground. Determine the average acceleration of the ball in m/s/s. Enter a numerical answer (no units) accurate ... .
(Note: Numbers are randomly generated and may differ from those shown here.)

Acceleration (a) is the rate of change in an object's velocity. It is determined from knowledge of a velocity change (Δv) and the change in time (Δt) over which the velocity changes.
a = Δvelocity / Δtime = Δv / Δt

The Minds On Physics program calculates answers accurate to several decimal places. Your answer does not need to be that precise. The program will allow you to have a 1% deviation from the right answer without being wrong. This means you should enter your answer to at least the second decimal place.