Page 59 - Math Course 3 (Book 2)

Surface Area of Pyramids and Cones

Mo. 8

Lesson 5 Key Concept

KEY CONCEPTS: Surface Area of Cone

1. Find surface areas of pyramids. Words The surface area S of a cone with slant
2. Find surface areas of cones. height and radius r is the lateral area
plus the area of the base.
Symbols S = L + B or S = r + r²

MO. 8 - L5a

Find Surface Area of Pyramids Model
and Cones

Vocabulary A-Z r

Let us learn some vocabulary

slant height
The altitude or height of each lateral face is called Let’s Begin
the slant height.

Vertex Surface Area of a Pyramid

lateral face Example
altitude

slant height base Find the surface area of the square pyramid.
First find the lateral area. The lateral area of the
pyramid is made up of four triangles.
Square Pyramid

8.9 ft

lateral face

8 ft
base

1
Estimate L = 4( )(8)(9) = 144
2
slant height 1
L = 4( )bh Area of 4 triangles
2
1
= 4( )(8)(8.9) Replace b with 8 and h with 8.9
2
Net of Square Pyramid
= 142.4 ft² Simplify.

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