Q21 of 37 Page 13

A field is in the form of a circle. The cost of ploughing the field at Rs. 1.50 per m2 is Rs. 5775. Find the cost of fencing the field at Rs. 8.50 per metre.

Cost of ploughing 1m2 of the field = Rs1.50


The total cost of ploughing the field = Rs 5775


So,




=3850m2


Given: A field is in the form of a circle.


Let the radius of the field = r


∴ Area of the field = πr2


⇒ 3850 = πr2




⇒ r2 = 1225


⇒ r = √1225


⇒ r = √(5×5×7×7)


⇒ r = 35m


Now,


Circumference = 2πr



= 2 × 22 × 5


= 220 m


Cost of fencing 1m of the field = Rs 8.50


Cost of fencing 220 of the field = Rs 8.50 × 220


= Rs 1870


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 20

The cost of fencing a circular field at the rate of Rs. 24 per metre is Rs. 5280. The field is to be ploughed at the rate of Rs. 0.50 per m2. Find the cost of ploughing the field

22

A chord of a circle of radius 10cm subtends a right angle at the centre. Use π=3.14 and find:

(i) area of the minor sector


(ii)area of the major sector

 23

In a circle of radius 21 cm, and arc subtends an angle of 60° at the centre. Find

(i) length of arc


(ii) area of the sector formed by the arc


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