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Ex 12.1, 4 - The wheels of a car are of diameter 80 cm each - Ex 12.1

Ex 12.1, 4 - Chapter 12 Class 10 Areas related to Circles - Part 2
Ex 12.1, 4 - Chapter 12 Class 10 Areas related to Circles - Part 3

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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 = (π‘‡π‘œπ‘‘π‘Žπ‘™ π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’)/(π·π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘π‘œπ‘£π‘’π‘Ÿπ‘’π‘‘ 𝑖𝑛 1 π‘Ÿπ‘’π‘£π‘œπ‘™π‘’π‘‘π‘–π‘œπ‘›) Diameter of circle = 80 cm radius = r = 80/2 = 40 cm Distance covered in one revolution = Circumference of wheel = 2 πœ‹r = 2 Γ—πœ‹Γ—40 = 80Ο€ cm Now, we find total distance covered We know that, Speed = π·π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’/(π‘‡π‘–π‘šπ‘’ ) Here, Speed = 66 km/hr Time = 10 minutes = 10/60 hour = 1/6 hour Putting value in formula 66 = Distance/(1/6) 66 Γ—1/6 = Distance 11 = Distance Distance = 11 km Distance = 11 km = 11 Γ— 1000 m = 11000 m = 11000 Γ—100 cm = 1100000 cm Now , Number of revolutions = (π‘‡π‘œπ‘‘π‘Žπ‘™ π‘‘π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’)/(π·π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘π‘œπ‘£π‘’π‘Ÿπ‘’π‘‘ 𝑖𝑛 1 π‘Ÿπ‘’π‘£π‘œπ‘™π‘’π‘‘π‘–π‘œπ‘›) = 1100000/80Ο€ = 110000/8Ο€ = 110000/(8 Γ— 22/7) = (110000 Γ— 7)/(8 Γ— 22) = 4375 Hence, number of revolutions = 4375

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Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 12 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.