A cylinder of height 12cm and radius 5cm is made of cardboard use the value of 3.1 to calculate the total surface area of the cardboard needed to make

a) a closed cylinder.
b) a cylinder open at one end

5 answers

I don't understand math lol
The surface area of a cylinder is height + 2(pi*r^2).

(pi*r^2) is the area at each end.

Is 3.1 the diameter or radius? 2r = D
The surface area of a cylinder is 2 pi rh + 2(pi*r^2).
I don't get it