Average Acceleration is the change in speed in a period of time .
so we here use the formula :
(Final speed-Initial speed)/time
N.B: rest is 0m/s as no movement so no speed.
=( 16km/hr - 0km/hr) / (3 divided by 3600)
*you have to change the seconds into hours to match with the speed or you can change the speed from km/hr to m/s , your choice . Here I changed the time by dividing over 3600 seconds because 1 hour contains 3600 sec right?
The final answer will be 19200 km/hr square .