6th Grade Math Textbook, Fundamentals

13.5 cm

22.5 cm

18 cm

5 cm

Lesson 11-3 for exercise sets. Chapter 11 307

Check Your Progress I

Use the formula to find the surface area of a triangular prism in which the

area of the triangular base is 108 yd^2 and each of the three rectangular faces

is 24 yards long and 15 yards wide.

S 2 BA 1 A 2 A 3 Formula for surface area of a rectangular prism

2(108) (24 • 15) (24 • 15) (24 • 15) Substitute known values.

2(108) 3(24 • 15) Simplify.

 216  1080

 1296

So the surface area of the triangular prism is 1296 square yards.

1

10 cm

6 cm

13 cm

8 cm Face 1 Face 2 Face 3

10 cm

6 cm

 13 cm

8 cm

h  8 cm b  6 cm

8 cm 6 cm

B

B

Key Concept

S 2 BA 1 A 2 A 3 , where Ssurface area,

Barea of the triangular base, A 1 area of rectangular face 1,

A 2 area of rectangular face 2, A 3 area of rectangular face 3.

Surface Area (S) of a Triangular Prism

Find the area of a base.

Find the area of the other faces.

Find the sum of the areas.

So the surface area of the triangular prism is 360 square centimeters

Find the surface area of a rectangular prism with the given dimensions.

1.10 m; w2.5 m; h14 m 2.3 in.; w2 in.; h5 in.

3.Draw a net of the triangular prism at the right and find its surface area.

4.Discuss and Write Explain how you would find the surface area

of a cube and then write a formula.

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2

You can also use a net to find the surface area of a triangular prism.

A bh (6)(8) 24 cm^2

Area of Face 1 h8 • 13 104 cm^2

Area of Face 2 w13 • 10 130 cm^2

Area of Face 3 b13 • 6 78 cm^2

2(24)  104  130  78  48  312 360 cm^2

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