Question: what is the surface area of the composite figure?
Answer: Let's say the triangular prism has a length of 8 inches, a width of 8 inches, a height of 3 inches and a side length of 5 inches. Using the formula for surface area of a triangular prism, SA = wh + lw + lh + ls, we calculate a surface area of 152 square inches. Step 3: Subtract the overlapping parts from each figure.