To find the surface area of a triangular prism, first find the lateral area. The lateral area is the product of the perimeter of the base and the height. The perimeter of the base is 15 in.+20 in.+25 in.=60 in., so the lateral area is 60 in.⋅30 in.=1800 in.2. The surface area of any prism is the lateral area plus the base area. Because each base is a right triangle, the area of each base is 12bh. Because the legs of the right triangle are perpendicular, you can use one of them as the base and one as the height. So, the base area is 12⋅20 in.⋅15 in.=150 in.2. There are two bases, so the surface area is 1800 in.2+150 in.2+150 in.2=2100 in.2.
