Transcript surface area - mjonesdriftwood

10.5
Surface Areas of Prisms and Cylinders
Skill Check
Lesson Presentation
Lesson Quiz
10.5
Surface Areas of Prisms and Cylinders
Skill Check
Find the area of a rectangle having the given length
and width.
1. length: 4 in., width: 7 in.
28 in.2
2. length: 12 in., width: 20 in.
240 in.2
3. length: 30 in., width: 40 in.
1200 in.2
4. length: 2.5 in., width: 5.5 in.
13.75 in.2
10.5
Surface Areas of Prisms and Cylinders
Pizza Box The surface area of a solid is the
sum of the areas of its faces. The pizza box
shown has the shape of a rectangular prism.
What is its surface area?
In Example 1, a net is used to find the surface area of the pizza box.
A net is a two-dimensional representation of a solid. The surface
area of a solid is equal to the area of its net.
10.5
Surface Areas of Prisms and Cylinders
EXAMPLE
1
Using a Net to Find Surface Area
The net at right represents the pizza box shown on the previous
slide. (Any flaps or foldovers to hold the box together have been
ignored.) Use the net to find the surface area of the pizza box.
SOLUTION
1
Find the area of each face.
Area of top or bottom:
16 • 16 = 256 in. 2
Area of each side: 16 • 2 = 32 in. 2
2
Find the sum of the areas of the faces.
256 + 256 + 32 + 32 + 32 + 32 = 640 in. 2
ANSWER
The surface area of the pizza box is 640 square inches.
10.5
Surface Areas of Prisms and Cylinders
Surface Areas of Prisms The lateral faces of a prism are the faces that
are not bases. The lateral area of a prism is the sum of the areas of the
lateral faces. The surface area of a prism is the sum of the areas of the
bases and the lateral area. In the diagram, P is the base perimeter.
Surface area
=
2 • Base area
+
Lateral area
=
2B
+
Ph
=
+
10.5
Surface Areas of Prisms and Cylinders
Surface Area of a Prism
Words The surface area S of a prism is the sum of twice the
base area B and the product of the base perimeter P and the
height h.
Algebra S = 2B + Ph
Numbers
S = 2(6 • 4) + [2(6) + 2(4)]10 = 248 square units
10.5
EXAMPLE
Surface Areas of Prisms and Cylinders
2
Using a Formula to Find Surface Area
Find the surface area of the prism.
The bases of the prism
are right triangles.
S = 2B + Ph
1
Write formula for surface area.
= 2( 2 • 6 • 8) + (6 + 8 + 10)(18)
Substitute.
= 480
Simplify.
ANSWER
The surface are of the prism is 480 square centimeters.
10.5
Surface Areas of Prisms and Cylinders
Surface Areas of Cylinders The curved surface of a cylinder is called the
lateral surface. The lateral area of a cylinder is the area of the lateral
surface. The surface area of a cylinder is the sum of the areas of the bases
and the product of the base circumference and the height. In the diagram
below, C represents the base circumference.
Surface area
=
2 • Base area
+
Lateral area
=
2B
+
Ch
=
+
10.5
Surface Areas of Prisms and Cylinders
Surface Area of a Cylinder
Words The surface area S of a cylinder is the sum of twice the
base area B and the product of the base circumference C and
the height h.
Algebra S = 2B + Ch = 2πr 2 + 2πrh
Numbers
S = 2π(4) 2 + 2π(4)(10)
352 square units
10.5
Surface Areas of Prisms and Cylinders
EXAMPLE
3
Using a Formula to Find Surface Area
Racquetball Find the surface area of the container of
racquetballs. Round to the nearest square inch.
SOLUTION
The radius is one half of the
diameter, so r = 1.25 inches.
S = 2πr 2 + 2πrh
Write formula for surface area of a cylinder.
= 2π(1.25) 2 + 2π(1.25)(5)
Substitute.
= 15.625π
Simplify.
49.1
ANSWER
Evaluate. Use a calculator.
The surface area of the container of racquetballs is
about 49 square inches.
10.5
Surface Areas of Prisms and Cylinders
Lesson Quiz
Find the surface area of the solid. Round to the nearest
whole number.
1. A rectangular prism with a height of 16 inches and a
base of length 3 inches and width 4 inches 248 in.2
2. A cylinder with radius 2 meters and height 14 meters
201 m2
3. Find the lateral area of a pipe with diameter 6 feet
and length 60 feet. Round to the nearest square foot.
1131 ft2
4. Challenge You have a cylindrical rod that has a radius
of 1 inch and is 12 inches long. If you cut the rod into
three pieces of the same size, by how much would the
total surface area increase? about 12.6 in.2