How to Find the surface area of a sphere

In this tutorial the instructor shows how to find the surface area of a sphere. He explains the equation to calculate the surface area of a sphere as 4 * Pi * r * r , where r its the radius of the sphere. Now if you have the radius of the sphere, by substituting its value in this equation and substituting the value of Pi, you can obtain the surface area of a sphere. If you want to compute the surface area of a sphere watch this video where it is clearly explained how to compute it along with an example.