RS Aggarwal - Mathematics

Book: RS Aggarwal - Mathematics

Chapter: 18. Area of Circle, Sector and Segment

Subject: Maths - Class 10th

Q. No. 20 of Formative Assessment (Unit Test)

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20

A square tank has an area of 1600 m2. There are four semicircular plots around it. Find the cost of turfing the plots at Rs. 12.50 per m2. [Take π = 3.14]

Let the length of side of the square tank be a


Area of square tank = a2 = 1600 m2


a = √1600 m = 40 m



Let the radius of semicircle be R


From the figure we can see that


Length of the side of the square = Diameter of semicircle


40 m = 2 × R


R = 40/2 m


R = 20 m


Area of semi-circle = 1/2 R2 = 1/2 × 3.14 × 20 × 20 m2


= 628 m2


Area of 4 semi-circles = 4 × 628 m2


= 2512 m2


Cost of turfing the plots = Rs. 12.50 per m2


Cost of Turfing = Cost of turfing per m2 × Area of 4 semicircle


= Rs. 12.50 × 2512


= Rs. 31400


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