The lateral surface area of a cone is
(pi) x (radius of the base) x (slant height) .
You can't double pi. But if you double the radius of the base
and keep the same slant height, OR double the slant height
and keep the same radius, then the lateral area will double.
More generically . . . if you increase the radius and the slant
height in any way that doubles their product, then the lateral
area doubles.
