How do you get the outer surface area of a cylinder?

Answer 1

Think of slitting the cylinder down one side, then unroll it and lay it down flat.

What you have then is a rectangle. The area of the rectangle is: (length x width).

The length of the rectangle used to be the length of the cylinder, and the width of

the rectangle used to be the circumference of the circle at the end of the cylinder,

which is (pi) x (diameter of the cylinder), or (pi) x (double the radius of the cylinder).

We're sure you can do it now.