The wheels of a car are of diameter 80 cm each. How many complete revolutions does each wheel make in 10 minutes, when the car is travelling at a speed of 66 km per hour?

Given
Diameter of wheel(D)=80cm
Radius(r)=80/2=40cm.
1 complete revolution of wheel = Circumference of wheel (C)
C=2πr=2π×40=80πcm
C=0.8πm
Speed of the car=66km / hr.=66×1000/60m/ min.
∴Speed of the car=1100m / min.
Therefore, in 10min., the car will travel a distance of
1100×10=11000m
No. of revolutions of wheel=11000/0.8π=11000×7/0.8×22=4375
Each wheel of the car makes 4375 complete revolutions in 10 min.