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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 m^{2}. Find the cost of ploughing the field.

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#### 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

= πr^{2}

= `(22)/(7) xx 35 xx 35`

= 3850m^{2}

Thus, the cost of ploughing the field at the rate of Rs.15/m^{2}

= Rs.15 x 3850

= Rs.57750.

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