Page 519 - Basic College Mathematics with Early Integers

496 C HAPTE R 6 I PERCENT

Definitions and Concepts Examples
Section 6.2 Solving Percent Problems Using Equations

Three key words in the statement of a percent problem Solve:
are 6 is 12% of what number?
#
of, which means multiplication 1 2 T T T T T
is, which means equals 1 = 2 6 = 12% # n
what (or some equivalent word or phrase), which 6 = 0.12 # n Write 12% as a decimal.
stands for the unknown number 6
= n Divide 6 by 0.12, the number
0.12 multiplied by n.
50 = n
Thus, 6 is 12% of 50.

Section 6.3 Solving Percent Problems Using Proportions

PERCENT PROPORTION Solve:
20.4 is what percent of 85?
amount percent
= T T T
base 100 ; always 100
amount percent base
or
amount : a p ; percent amount : 20.4 = p ; percent
= base : 85 100
base : b 100
#
#
20.4 100 = 85 p Set cross products equal.
#
2040 = 85 p Multiply.
2040
= p Divide 2040 by 85, the number
85 multiplied by p.
24 = p Simplify.
Thus, 20.4 is 24% of 85.
Section 6.4 Applications of Percent

PERCENT OF INCREASE A town with a population of 16,480 decreased to 13,870
over a 12-year period. Find the percent decrease. Round
amount of increase
percent of increase = to the nearest whole percent.
original amount
amount of decrease = 16,480 - 13,870
= 2610
PERCENT OF DECREASE amount of decrease
percent of decrease =
amount of decrease original amount
percent of decrease =
original amount 2610
= L 0.16
16,480
= 16%
The town’s population decreased by 16%.

Section 6.5 Percent and Problem Solving: Sales Tax, Commission, and Discount

SALES TAX AND TOTAL PRICE Find the sales tax and the total price of a purchase of $42
if the sales tax rate is 9%.
#
sales tax = sales tax rate purchase price
sales tax = sales tax rate # purchase price
total price = purchase price + sales tax Copyright 2012 Pearson Education, Inc.
T T T
sales tax = 9% # $42
#
= 0.09 $42
= $3.78