If dealing with 3D shapes you might be asked to find the surface area of a shape. One way may be to look at its net.
A net is just a 3D shape folded flat. E.g. here is the net of a square.In a questions you can find the surface area just by adding up all the areas of the shapes that make the net.
Surface Area Of A Sphere
Surface area of a sphere = 4πr2
Surface Area Of A Cone
Surface area of a cone = πrl + πr2
Note: l is the slanted height.Surface Area Of A Cylinder
Surface area of a cylinder = 2πrh + 2πr2