Question

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

(A) 2πr (l + r)
(B) πr (l + 4 r )
(C) πr (l + r)
(D) 2πrl​
please answer urgent

Answer 1

`A=4\pi r(l+r)`

Explanation:

The total surface area of a cone is given by :

`A=\pi rl+\pi r^2\\\\=\pi r(l+r)`

Put r = 2r and l = 2l in the above formula

`A=\pi * 2r(2l+2r)\\\\A=2\pi r(2l+2r)\\\\=2\pi r * 2(l+r)\\\\=4\pi r(l+r)`

Hence, the total surface area of the cone is
`4\pi r(l+r)`.