Question

The total surface area of a cone of radius  `r/2` and length 2l, is

विकल्प

• `2 pi r (1 + r)`

• ` pi r (1 + r/4)`

• `pi r (1+ r) `

• ` 2 pi rl`

Answer 1

The formula of the total surface area of a cone with base radius ‘r’ and slant height ‘l’ is given as

Total Surface Area = `pi r(l+r)`

Here it is given that the base radius is ‘`r/2`’ and that the slant height is ‘2l’.

Substituting these values in the above equation we have

Total Surface Area = `pi (r/2)(2l+r/2)`

= `pir(l+r/4)`