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  1. Chapter 11 Class 8 Mensuration
  2. Serial order wise

Transcript

Example 6 In a building there are 24 cylindrical pillars. The radius of each pillar is 28 cm and height is 4 m. Find the total cost of painting the curved surface area of all pillars at the rate of Rs 8 perγ€– π‘šγ€—^2. Given, Height of each pillar = 4 cm & Radius of each pillar = 28 cm = 28/100 m To find cost of painting the pillars, We find Curved Surface area of pillars Curved Surface Area of Pillar Curved Surface Area = 2Ο€rh = 2 Γ— 22/7 Γ— 28/100 Γ— 4 = 2 Γ— 22 Γ— 4/100 Γ— 4 = 44 Γ— 16 Γ— 1/100 = 704/100 m2 Now, there are 24 pillars So, Total Surface area to be painted = 24 Γ— Curved Surface Area of 1 pillar Total Surface area to be painted = 24 Γ— Curved Surface Area of 1 pillar = 24 Γ— 704/100 = 16896/100 = 168.96 m2 Now, Cost of painting is Rs 8 perγ€– π‘šγ€—^2 So, Cost of painting per 1 m2 = Rs 8 Cost of painting per 168.96 m2 = Rs 8 Γ— 168.96 = Rs 8 Γ— 16896/100 = Rs 135168/100 = Rs 1351.68

About the Author

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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.