The time it takes a spinner to stop completely is 12 seconds. if the spinner completes 6 revolutions in this time, what was the average angular velocity of the spinner, in radians per second, for the 12-second interval?

The angular velocity by definition is given by:
 w = rev / t
 Where:
 rev: revolutions
 t: time
 Substituting values we have:
 w = (6 * (2 * pi)) / (12)
 w = 3.141592654 rad / s
 
 the average angular velocity of the spinner, in radians per second, for the 12-second interval is:
 w = 3.141592654 rad / s