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12.2 Surface Area of Prisms and Cylinders. Hubarth Geometry. The surface area of a polyhedron is the sum of the areas of its faces. Ex 1 Find The Surface Area of the Prism. Find the surface area of the rectangular prism. 5in. 3in. 8in. Solution.
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12.2 Surface Area of Prisms and Cylinders Hubarth Geometry
The surface area of a polyhedron is the sum of the areas of its faces. Ex 1 Find The Surface Area of the Prism Find the surface area of the rectangular prism. 5in 3in 8in Solution Add the area of all the rectangles that form the faces of the prism. Congruent Faces Dimensions Area of Face Left face and right face 3in by 5in 3 X 5= 15in2 Front face and back face 8in by 5in 8 X 5 = 40in2 Top face and bottom face 8in by 3in 8 X 3 = 24in2 Area= 158 square inches
Lateral Faces and Area The lateral faces of a prism are the faces of the prism that are not bases. Lateral area is the sum of the areas of the lateral faces. Theorem 12.2 Surface Area of a Right Prism Words Surface area= 2(area of base) + (perimeter of base)(height) Symbols S=2B + Ph h w l
Ex 2 Find Surface Area of a Prism 6m Find the surface area of the prism. 4m 3m 5m 7m Solution
A cylinder is a solid with two congruent bases that lie in Parallel planes. The lateral area of a cylinder is the area of the curved surface. Radius r base . Lateral surface Height h base
Surface = 2(area of base) + lateral area area = + r r = h h + r r
Theorem 12.3 Surface Area of a Right Cylinder h r
Ex 3. Find Surface Area of a Cylinder Find the surface area of the cylinder. Round your answer to the nearest whole number. 4ft 3ft Solution
Find the height of the right cylinder shown, which has a surface area of 157.08 square meters. Ex 3 Find the Height of a Cylinder Substitute known values in the formula for the surface area of a right cylinder and solve for the height h. S = 2πr2 + 2πrh 157.08 = 2π(2.5)2 + 2π(2.5)h 157.08 = 12.5π + 5πh 157.08 – 12.5π = 5πh 117.81 ≈ 5πh 7.5 ≈ h
Practice Find the surface area of the prism. 10cm 1. 2. 3in 4cm 8cm 6cm 6in 2in 3. Find the surface area of the cylinder 10ft 12 ft