You can put this solution on YOUR website! A cylinder is composed of two "bases" and another surface. Hence the surface area is equal to the sum of these areas.
For example, if you have a right circular cylinder with radius r and height h, the areas of the bases would be because we have two circles.
The area of the remaining surface would be equal to the circumference of the base, times the height (this is because if we were to unfold it, we would obtain a rectangle with those dimensions). Therefore this area would be .
