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Ex 11.3, 8 - Find the cost of polishing a circular table-top of

Ex 11.3, 8 - Chapter 11 Class 7 Perimeter and Area - Part 2
Ex 11.3, 8 - Chapter 11 Class 7 Perimeter and Area - Part 3

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Ex 9.2, 8 Find the cost of polishing a circular table-top of diameter 1.6 m, if the rate of polishing is Rs 15/m2. (Take Ο€ = 3.14) Here, Area to be polished = Area of circular table top Diameter = 1.6 m Radius = r = π·π‘–π‘Žπ‘šπ‘’π‘‘π‘’π‘Ÿ/2 = 1.6/2 = 16/(2 Γ— 10) = 8/10 m Area of table top = πœ‹r2 = 3.14 Γ— (8/10)^2 = 314/100 Γ— 8/10 Γ— 8/10 = (314 Γ— 64)/10000 = 20096/10000 = 2.0096 m2 Now, Cost of polishing 1 m2 area = Rs 15 Cost of polishing 2.0096 m2 area = Rs 15 Γ— 2.0096 = Rs 15 Γ— 20096/10000 = Rs 3 Γ— 20096/2000 = Rs 3 Γ— 10048/1000 = Rs 30144/1000 = Rs 30.144 = Rs 30.14 (approx.) ∴ It will cost Rs 30.14 (approx.) to polish the table top

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