Question

The diameter of the base of a cone is $10.5\mathrm{cm}$ and its slant height is $10\mathrm{cm}$. Find its curved surface area (Assume $\mathrm{\pi }=\frac{22}{7}$)

Answer 1

Finding CSA of Cone.

It is given that, the diameter of the base$\left(d\right)$ is $10.5\mathrm{cm}$and its slant height $\left(l\right)$ is $10\mathrm{cm}$.

The radius of the base$\left(r\right)=\frac{10.5}{2}=5.25\mathrm{cm}\left[\because r=\frac{d}{2}\right]$

The curved surface area of the cone is computed as follows:

$$\begin{gathered} \mathrm{C}.\mathrm{S}.\mathrm{A}=\mathrm{\pi }rl \\ \Rightarrow \mathrm{C}.\mathrm{S}.\mathrm{A}=\frac{22}{7}\times 5.25\times 10 \\ \Rightarrow \mathrm{C}.\mathrm{S}.\mathrm{A}=\frac{1155}{7} \\ \Rightarrow \mathrm{C}.\mathrm{S}.\mathrm{A}=165{\mathrm{cm}}^2 \end{gathered}$$

Hence, the curved surface area of the cone is $165{\mathrm{cm}}^2$.