Question

The total surface area of a cone whose radius is `r/2` and slant height 2l is ______.

Options

• `2pir (l + r)`

• `pir (l + r/4)`

• `pir(l + r)`

• `2pirl`

Answer 1

The total surface area of a cone whose radius is `r/2` and slant height 2l is `underlinebb(pir (l + r/4))`.

Explanation:

The formula of total surface area of cone = Area of the base + Curved surface area of cone

= `pi(r/2)^2 + pi(r/2) xx 2l`

= `(pir)/2 (r/2 + 2l)`

= `(pir)/2 (r + 4l)`

= `pir(l + r/4)`