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Question
The cost of fencing a circular field at the rate of Rs.250 per metre is Rs.55000. The field is to be ploughing at the rate of Rs.15 per m2. Find the cost of ploughing the field.
Solution
Let the radius of the circular field = r m
⇒ Circumference of the field = 2πr m
Now, the cost of fencing the circular field at Rs.250/m = Rs.55000
⇒ 2πr x 250 = 55000
⇒ `2 xx (22)/(7) xx "r" xx 250` = 55000
⇒ r = `(55000 xx 7)/(2 xx 22 xx 250)`
= 35m
Now, the area of the field
= πr2
= `(22)/(7) xx 35 xx 35`
= 3850m2
Thus, the cost of ploughing the field at the rate of Rs.15/m2
= Rs.15 x 3850
= Rs.57750.
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