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Example 1: The cost of fencing a circular field at the rate of Rs 24 per metre isRs 5280. The field is to be ploughed at the rate of Rs 0.50 per m'. Find the cost ofploughing the field (Take t= ).100 |
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Answer» Length of the fence (in metres) = Total cost / Rate = 5280/24 = 220 So, circumference of the field = 220 m Therefore, if r metres is the radius of the field, then 2πr = 220 or, 2 × 22/7× r = 220 or, r = (220 × 7)/(2 × 22) = 35 i.e., radius of the field is 35 m. Therefore, area of the field = πr2 = 22/7 × 35 × 35 m2 = 22 × 5 × 35 m2 Now, cost of ploughing 1 m2 of the field = Rs 0.50 So, total cost of ploughing the field = Rs 22 × 5 × 35 × 0.50 = Rs 1925 |
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