Question

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

Answer 1

Answer:

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

Step-by-step 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

$A=\pi \times 2r(2l+2r)\\\\A=2\pi r(2l+2r)\\\\=2\pi r \times 2(l+r)\\\\=4\pi r(l+r)$

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