I have had a few of these questions (both volume and surface area) and not comfortable with changing the formula over. Any help is appreciated to logical steps for this and other such problems
A cone has radiusr and slant height l.
A cylinder has radius r and height r.
The total surface area of the cone is equal to the total surface area of the cylinder.
Find an expression for l in terms of r.
If you plug "r" in for "h" (because h = r) in , what do you get? (Plug "r" in for "h" in the formula you were given, simplify, and note the result.)
If you solve for , what do you get? (Divide through by and then solve the resulting literal equation.)
If you get stuck, please reply showing how far you have gotten. Thank you!