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Question 4 - Area and Circumference of Circle - Chapter 11 Class 10 Areas related to Circles

Last updated at May 29, 2023 by

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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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? 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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