Page 686 - Basic College Mathematics with Early Integers

S E C T I O N 9.5 I VOLUME AND SURFACE AREA 663

32
The volume of the sphere is exactly p cubic inches or approximately
11 3
33 cubic inches.
21
SA = 4pr 2 Formula for surface area
#
SA = 4 p(2 in.) 2 Let r = 2 inches.
= 16p sq in. Exact surface area
22 22
L 16 # sq in. Approximate with .
p
7 7
352 2
= or 50 sq in. Approximate surface area
7 7
The surface area of the sphere is exactly 16p square inches or approximately
2
50 square inches.
7
Work Practice 2

1
Example 3 Approximate the volume of a can that has a 3 -inch radius and a PRACTICE 3
22 2 Approximate the volume of a
height of 6 inches. Use for p. Give an exact volume and an
7 cylinder of radius 5 inches and
approximate volume.
height 9 inches. Use 3.14 for p.
3q in. Give an exact answer and an
approximate answer.

6 in.

Solution: Using the formula for a circular cylinder, we have
# 2 #
V = p r h
1 7
3 =
2 2
Î 2
7
# #
= p a in.b 6 in.
2
49
#
= p # sq in. 6 in.
4
1
# # #
p 49 2 3
= cu in.
#
2 2
1
1
= 73 p cu in. or 73.5p cu in.
2
22
This is the exact volume. To approximate the volume, use the approximation
7
for p.
1 147 22 22
V = 73 p or # cu in. Replace with .
p
2 2 7 7
1 1
21 # # #
2 11
7
= # cu in.
2 7
1 1
= 231 cubic in.
The volume is approximately 231 cubic inches. Answer
Work Practice 3 3. 225p cu in. L 706.5 cu in.