6th Grade Math Textbook, Fundamentals

w



h

Key Concept

S 2 w 2 h 2 wh, where Ssurface area,

length, wwidth, and hheight.

Surface Area (S) of a Rectangular Prism

306 Chapter 11

11-3

  12 in.

w  8 in.

h  4 in.

  12 in.

h  4 in.

w  8 in.

top

w



h

back bottom

side

side

Remember:A net is a two-dimensional front

shape that can be folded to form a three-

dimensional object.

Think

A rectangular prism has three pairs of congruent faces.

Area of top Area of bottom

Area of front Area of back

Area of left side Area of right side

Method 1Find the area of each face.

Then add the areas.

Area of top w12 • 8  96

Area of bottom w12 • 8  96

Area of front h12 • 4  48

Area of back h12 • 4  48

Area of left side wh8 • 4  32

Area of right side wh8 • 4  32

96  96  48  48  32  32

2(96) 2(48) 2(32)

192  96  64

352 in.^2

Method 2Use a formula.

S 2 w 2 h 2 wh,

where Ssurface area, length,

wwidth, and hheight.

12 in. w8 in. h4 in.

S2(12)(8) 2 (12)(4) 2(8)(4)

2(96) 2(48) 2(32)

 192  96  64

352 in.^2

Update your skills. See page 410.

Surface Area of Prisms

Objective To draw and use nets to find the surface area of prisms

• To use formulas to find the surface area of prisms

Samuel is using construction paper to cover a grab-bag
box for a class party. The box has the same dimensions
as the box shown at the right. How many square inches
of construction paper does he need to cover the box
completely?

To find how much construction paper Samuel needs,

find the surface area of the prism.

The of a prism is the sum of the

areas of its faces. A net can help you visualize

the faces. You can find the surface area of a

prism by finding the area of its net.

surface area

So Samuel needs at least 352 square inches of construction paper

to cover the box completely.