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  1. Chapter 11 Class 7 Perimeter and Area
  2. Serial order wise

Transcript

Ex 11.3, 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 ฯ€ = 3.14) Here, Area to be polished = Area of circular table top Diameter = 1.6 m Radius = r = ๐ท๐‘–๐‘Ž๐‘š๐‘’๐‘ก๐‘’๐‘Ÿ/2 = 1.6/2 = 16/(2 ร— 10) = 8/10 m Area of table top = ๐œ‹r2 = 3.14 ร— (8/10)^2 = 314/100 ร— 8/10 ร— 8/10 = (314 ร— 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 ร— 2.0096 = Rs 15 ร— 20096/10000 = Rs 3 ร— 20096/2000 = Rs 3 ร— 10048/1000 = Rs 30144/1000 = Rs 30.144 = Rs 30.14 (approx.) โˆด It will cost Rs 30.14 (approx.) to polish the table top

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Davneet Singh
Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 8 years. He provides courses for Maths and Science at Teachoo. You can check his NCERT Solutions from Class 6 to 12.