Number of revolutions = (Total distance)/(Distance covered in one revolutions)
Radius of the circle = 80/2 = 40 cm
Distance covered in one revolution = Circumference of the wheeel = 2πr
= 80π cm
Distance covered = speed x time = 66*(1/6) = 11 km = 1100000 cm
Number of revolutions = (1100000)/ (80π)= 4375 revolutions