Surface Area of a Right Circular Cone

_____${\mathrm{m}}^2$ of canvas is required for a conical tent whose height is $3.5\mathrm{m}$ and the radius of the base is $12\mathrm{m}?$

A cloth having an area of $165 {\mathrm{m}}^2$ is shaped into the form of a conical tent of radius $5 \mathrm{m}$

(i) How many students can sit in the tent if a student, on a average occupies $\frac{5}{7} {\mathrm{m}}^2$ on the ground?

(ii) Find the volume of the cone.

A right triangle with sides $6 \mathrm{cm}, 8 \mathrm{cm}$ and $10 \mathrm{cm}$ is revolved about the side $8 \mathrm{cm}.$ Find the volume and the curved surface area of the solid so formed.

If the radius of cylinder is doubled and its curved surface area is not changed, the height must be halved.

In a right circular cone, height, radius and slant height do not always be sides of a right triangle.

The total surface area of a cone whose radius is $\frac{r}{2}$ and slant height $2l$ is