Page 327 - Basic College Mathematics with Early Integers

304 C HAPTE R 4 I DECIMALS

PRACTICE 11 Example 11 In 2050, the 451.8 million in 2050
In 2007, there were 60.7 million population of
married couples in the United the United States is projected to
States.Write this number in be 451.8 million. Write this
standard notation. number in standard notation.
(Source: U.S. Census Bureau) (Source: U.S. Census Bureau)

Solution: 451.8 million = 451.8 * 1 million
= 451.8 * 1,000,000 = 451,800,000
Work Practice 11

Objective Using Decimals as Replacement Values

Now let’s practice working with variables.

PRACTICE 12 Example 12 Evaluate xy for x = 2.3 and y = 0.44.
Evaluate 7y for y =-0.028.
#
Solution: Recall that xy means x y.
xy = (2.3)(0.44) 2.3
* 0.44
92
920

= 1.012 — 1.012
Work Practice 12

Objective Finding the Circumference of a Circle

Recall from Section 1.3 that the distance around a polygon is called its perimeter.
The distance around a circle is given the special name circumference, and this dis-
tance depends on the radius or the diameter of the circle.

Circumference of a Circle

Radius r

Diameter d

# #
#
Circumference = 2 p radius or Circumference = p diameter
C = 2pr or C = pd

In Section 4.1, we learned about the symbol as the Greek letter pi, pronounced
p
“pie.” It is a constant between 3 and 4.A decimal approximation for is 3.14.Also, a Copyright 2012 Pearson Education, Inc.
p
22
p
fraction approximation for is .
7
Answers
11. 60,700,000 12. -0.196