Question

A square tank has an area of 1600 cm². There are four semicircular plots around it. Find the cost of turfing the plots at Rs 12.50 per m².

Answer 1

Let a m be the side of the square.
Area of the square$=a^2$
Thus, we have:
$$\begin{gathered} a^2=1600 \\ \Rightarrow a=40 \end{gathered}$$
Area of the plots = 4(Area of the semicircle of radius 20 m)
$$\begin{gathered} =\left|4\left(\frac{1}{2}\mathrm{\pi }{r}^2\right)\right|{\text{m}}^2 \\ =\left|4\left(\frac{1}{2}\times 3.14\times 20\times 20\right)\right|{\text{m}}^2 \\ =2512{\text{m}}^2 \end{gathered}$$

∴ Cost of turfing the plots at $12.50{\text{per m}}^2=\text{Rs}\left(2512\times 12.50\right)$
= Rs 31400