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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Transcript

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 = (𝑇𝑜𝑡𝑎𝑙 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒)/(𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑐𝑜𝑣𝑒𝑟𝑒𝑑 𝑖𝑛 1 𝑟𝑒𝑣𝑜𝑙𝑢𝑡𝑖𝑜𝑛) Diameter of circle = 80 cm radius = r = 80/2 = 40 cm Distance covered in one revolution = Circumference of wheel = 2 𝜋r = 2 ×𝜋×40 = 80π cm Now, we find total distance covered We know that, Speed = 𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒/(𝑇𝑖𝑚𝑒 ) Here, Speed = 66 km/hr Time = 10 minutes = 10/60 hour = 1/6 hour Putting value in formula 66 = Distance/(1/6) 66 ×1/6 = Distance 11 = Distance Distance = 11 km Distance = 11 km = 11 × 1000 m = 11000 m = 11000 ×100 cm = 1100000 cm Now , Number of revolutions = (𝑇𝑜𝑡𝑎𝑙 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒)/(𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑐𝑜𝑣𝑒𝑟𝑒𝑑 𝑖𝑛 1 𝑟𝑒𝑣𝑜𝑙𝑢𝑡𝑖𝑜𝑛) = 1100000/80π = 110000/8π = 110000/(8 × 22/7) = (110000 × 7)/(8 × 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 13 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.