Question

The slant height and base diameter of a conical tomb are $25m$ and $14m$ respectively. Find the cost of white-washing its curved surface at the rate of $Rs.210$ per $100m^2$.

Answer 1

Slant height of the cone $\left(l\right)=25m$

Diameter of base $\left(d\right)=14m$

$\Rightarrow$ Radius $\left(r\right)=\frac{14m}{2}=7m$

Curved surface area of the cone

$=\pi rl=\frac{22}{7}\times 7m\times 25m=550m^2$

Rate of white washing $=Rs.210$ per $100m^2$

Therefore, Total cost $=\frac{550m^2\times Rs.210}{100m^2}=55\times Rs.21=Rs.1155$

Therefore, the required amount is $Rs.1155$.