NAME _____________________________________________ DATE __________________ PERIOD _________
Lesson 5 Reteach
Surface Area of Cones
The lateral area L.A. of a cone is π times the radius times the slant height, or L.A. = πr. The total
surface area of a cone with slant height and radius r is the lateral area plus the area of the base,
or S.A. = L.A. + πr2 or S.A. = πr + πr2.
Example
Find the lateral and total surface areas of the cone.
Round to the nearest tenth.
Lateral Surface Area
Total Surface Area
L.A. = πrℓ
S.A. = L.A. + πr2
L.A. = π · 3 · 5
r = 3, = 5
L.A. ≈ 47.1
S.A. = 47.1 + π · 32
5 cm
3 cm
S.A. ≈ 75.4
The lateral and total surface areas of the cone are about 47.1 and 75.4 square centimeters.
Exercises
Find the lateral and total surface areas of each cone. Round to the
nearest tenth.
2.
1.
5.7 ft
Copyright © The McGraw-Hill Companies, Inc. Permission is granted to reproduce for classroom use.
10 cm
4 ft
4 cm
125.7 cm2; 175.9 cm2
3.
71.6 ft2; 121.9 ft2
4.
11.6 ft
7.3 ft
266.0 ft2; 433.4 ft2
Course 3 • Chapter 8 Volume and Surface Area
17 m
4m
213.6 m2; 263.9 m2
125