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Last updated at May 29, 2018 by Teachoo

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Ex 12.1, 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? Number of revolutions = (๐๐๐ก๐๐ ๐๐๐ ๐ก๐๐๐๐)/(๐ท๐๐ ๐ก๐๐๐๐ ๐๐๐ฃ๐๐๐๐ ๐๐ 1 ๐๐๐ฃ๐๐๐ข๐ก๐๐๐) Diameter of circle = 80 cm radius = r = 80/2 = 40 cm Distance covered in one revolution = Circumference of wheel = 2 ๐r = 2 ร๐ร40 = 80ฯ cm Now, we find total distance covered We know that, Speed = ๐ท๐๐ ๐ก๐๐๐๐/(๐๐๐๐ ) Here, Speed = 66 km/hr Time = 10 minutes = 10/60 hour = 1/6 hour Putting value in formula 66 = Distance/(1/6) 66 ร1/6 = Distance 11 = Distance Distance = 11 km Distance = 11 km = 11 ร 1000 m = 11000 m = 11000 ร100 cm = 1100000 cm Now , Number of revolutions = (๐๐๐ก๐๐ ๐๐๐ ๐ก๐๐๐๐)/(๐ท๐๐ ๐ก๐๐๐๐ ๐๐๐ฃ๐๐๐๐ ๐๐ 1 ๐๐๐ฃ๐๐๐ข๐ก๐๐๐) = 1100000/80ฯ = 110000/8ฯ = 110000/(8 ร 22/7) = (110000 ร 7)/(8 ร 22) = 4375 Hence, number of revolutions = 4375

Chapter 12 Class 10 Areas related to Circles

Class 10

Important Questions for Exam - Class 10

- Chapter 1 Class 10 Real Numbers
- Chapter 2 Class 10 Polynomials
- Chapter 3 Class 10 Pair of Linear Equations in Two Variables
- Chapter 4 Class 10 Quadratic Equations
- Chapter 5 Class 10 Arithmetic Progressions
- Chapter 6 Class 10 Triangles
- Chapter 7 Class 10 Coordinate Geometry
- Chapter 8 Class 10 Introduction to Trignometry
- Chapter 9 Class 10 Some Applications of Trignometry
- Chapter 10 Class 10 Circles
- Chapter 11 Class 10 Constructions
- Chapter 12 Class 10 Areas related to Circles
- Chapter 13 Class 10 Surface Areas and Volumes
- Chapter 14 Class 10 Statistics
- Chapter 15 Class 10 Probability

About the Author

Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 9 years. He provides courses for Maths and Science at Teachoo.