Let’s start off with Surface Area. Surface area is the combined measurement of all faces in a 3D shape. This usually applies to prisms, prisms are solid objects that have identical ends and flat faces.

Many different prisms have different formulas to solve them, but boiled down it’s simply finding the area of each face and combining them together.

Composite surface area isn’t very different either, composite surface area is when two prisms are glued together to have a sort of  “super-prism”, solving the surface area is similar but with a twist.

Let’s say these are the dimensions for our composite shape:

Rectangular Prism 1:

Length : 15mm

Height :8mm

Width : 10mm

Rectangular Prism 2:

Length :6mm

Height: 4mm

Width : 5mm

In order to find the surface area of a composite prism, you first need to find the surface area of both prisms

Rectangular Prism 1: 700mm

Rectangular Prism 2: 148mm

Let’s say Prism 2 is on top of Prism 1, and the side glued to Prism 1 is 30mm, since its already glued to Prism 1, then it’s practically vanished away from both prisms, so we have to subtract 30mm x2, one for the 30mm taken away from Prism 1, and again for Prism 2.

So we add together both surface areas

848mm

And subtract the 60mm

788mm

And there we go, that’s how you solve for composite surface area, the same process applies to different shapes, it doesn’t matter as long as you solve for the surface area and the side that’s attached to the bigger shape