# Transparency 8 Click the mouse button or press the Space Bar to display the answers.

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Transparency 8 Click the mouse button or press the Space Bar to display the answers.

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Example 8-2b Objective Find the surface areas of pyramids and cones

Example 8-2b Vocabulary Lateral face A triangular side of a pyramid

Example 8-2b Vocabulary Slant height The altitude or height of each lateral face of a pyramid

Example 8-2b Vocabulary Lateral area The sum of the areas of the lateral faces of a pyramid

Lesson 8 Contents Example 1Surface Area of a Pyramid Example 2Surface Area of a Cone

Example 8-1a Find the surface area of the triangular pyramid. First find the area of the base Base is a triangle Normally, would find area of triangle but the area is provided Area of base = 10.8 in 2

Example 8-1a Find the surface area of the triangular pyramid. Second find the lateral area Area of base = 10.8 in 2 Write formula for area of triangle Replace b with 5 in  5 in Replace h with 8 in  8 in Multiply numbers A = 20 Multiply units in 2

Example 8-1a Find the surface area of the triangular pyramid. There are 3 lateral sides and they all have the same dimensions Area of base = 10.8 in 2 Area of lateral side = 20 in 2 Add area of sides and base Surface Area = 70.8 in 2 Answer:

Example 8-1c Find the surface area of the square pyramid. Surface Area = 156 cm 2 Answer:

Example 8-2a Find the surface area of the cone. Round to the nearest hundredth. Write formula for surface area of a cone Replace r with 1.5 m Replace l with 4.5 m Replace r with 1.5 m S =  (1.5 m) (4.5 m) +  (1.5 m) 2

Example 8-2a Find the surface area of the cone. Round to the nearest hundredth. Follow order of operations P E MD AS Evaluate (1.5) 2 S =  (1.5 m)(4.5 m) +  (2.25 m 2 ) Multiply from left to right S = 21.21 m 2 S =  (1.5 m)(4.5 m) +  (1.5 m) 2 + 7.07 m 2 Add S = 28.28 m 2 Answer:

Example 8-2b Find the surface area of the cone. Round to the nearest hundredth. Answer: SA = 108.33 cm 2 *

End of Lesson 8 Assignment Lesson 7:8 Surface Area of Pyramids and Cones 3 - 14 All

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