NCERT Solutions for Class 10 Maths Chapter 12

Important NCERT Questions

Areas Related To Circles Class,

NCERT Books for Session 2022-2023

CBSE Board and UP Board Others state Board

EXERCISE 12.1

Page No:226

Questions No: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?

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Diameter of wheel = 80 cm

Radius of wheel (r) = 40 cm

Circumference of wheel = 2πr = 2π (40) = 80m cm

Speed of car = 66 km/hour = (66 × 10000)/60 cm/min = 110000 cm/min

Distance travelled in 10 minutes = 110000 x 10 1100000 cm

Let the wheel makes n revolutions in 10 minutes. Therefore,

n × Distance travelled in one revolution (circumference) = Distance travelled in 10 minutes

⇒ n × 80π = 1100000

⇒ n = (1100000)/80π = (1100000 x 7)/(80 x 22) = (35000)/8 = 4375

Hence, the wheel takes 4375 revolutions in 10 minutes.

Video explanation of the above question✌😀