# 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?

**Solution:**

We use the concepts of areas of the circle to solve the question along with the formula of speed.

Distance traveled by the wheel in one revolution is the circumference of the wheel itself.

The diameter of the wheel of the car = 80 cm.

The radius of the wheel of the car = 40 cm

Distance travelled after 1 revolution = Circumference of the wheel

Circumference of the wheel = 2πr

= 2π (40) = 80π cm

Speed of car = 66 km/hour

= (66 × 100000)/60 cm/min

= 110000 cm/min

Distance traveled by car in the duration of 10 minutes

= 110000 × 10

= 1100000 cm

Let the number of revolutions of the wheel of the car be equal to n.

n × Distance traveled after 1 revolution = Distance traveled after 10 minutes

n × 80π = 1100000

n = (1100000 × 7)/(80 × 22)

= 35000/8

= 4375

Hence, each of the wheels of the car will make 4375 revolutions.

**Video Solution:**

## 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?

### NCERT Solutions Class 10 Maths - Chapter 12 Exercise 12.1 Question 4:

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?

Each wheel of the car makes 4375 revolutions in 10 minutes if the wheels of the car are of diameter 80 cm each and the car is traveling at a speed of 66 km per hour