Question

Find the cost of polishing a circular table-top of diameter $1.6\mathrm{m}$, if the rate of polishing is $₹15$ per ${\mathrm{m}}^2$. (Take $\mathrm{\pi }=3.14$)

Answer 1

Step 1: Calculate area of circular table-top

Given, diameter of circular table-top, $\mathrm{d}=1.6\mathrm{m}$

So, radius of the table-top, $\mathrm{r}=\frac{\mathrm{d}}{2}=\frac{1.6}{2}=0.8\mathrm{m}$

Area of a circle is given as,

$\mathrm{area}={\mathrm{\pi r}}^2$

Thus area of the table-top is,

$$\begin{gathered} \mathrm{area}={\mathrm{\pi r}}^2 \\ =3.14\times 0.8^2 \\ \approx 2.01{\mathrm{m}}^2 \end{gathered}$$

Step 2: Calculate cost of polishing

Cost for polishing $1{\mathrm{m}}^2$ area = $₹15$

Cost for polishing $2.01{\mathrm{m}}^2$ area = $15\times 2.01=₹30.15$

Therefore, the cost of polishing the table-top is $₹30.15$