A square tank has an area of 1600 m^{2}. There are four semicircular plots around it. Find the cost of turfing the plots at Rs. 12.50 per m^{2}. [Take π = 3.14]

Let the length of side of the square tank be a

Area of square tank = a^{2} = 1600 m^{2}

⇒ 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 R^{2} = 1/2 × 3.14 × 20 × 20 m^{2}

= 628 m^{2}

Area of 4 semi-circles = 4 × 628 m^{2}

= 2512 m^{2}

Cost of turfing the plots = Rs. 12.50 per m^{2}

Cost of Turfing = Cost of turfing per m^{2} × Area of 4 semicircle

= Rs. 12.50 × 2512

= Rs. 31400

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