Once you know how to calculate the surface area of just about any polyhedron you're gong to apply it to different problems where you've got some joined surfaces.

When solids are joined together, such as a hemisphere on a cone, the surface area of the connecting circle is not included in the overall surface area - it is "hidden." Thus, to solve **surface area of joined solids** problems, determine which faces or bases are hidden and find the surface area of the remaining parts.

Find the surface area:

In this one you have a cone joined to a cylinder. Thus,

SA=L.A_{co}+L.A_{cy}+A_{cir}

(The common mistake when you're trying to find the surface area is either adding in 2 circles because you see 2 circles or even 3 circles)