Intermediate Algebra (11th edition)

Since 39.3% was spent on food, let this amount in billions of dollars.

Multiply by 41.2.

Nearest tenth

Therefore, about $16.2 billion was spent on pet food. NOW TRY

OBJECTIVE 4 Solve problems involving percent increase or decrease.

Percent is often used to express a change in some quantity. Buying an item that has been

marked up and getting a raise at a job are applications of percent increase. Buying an

item on sale and finding population decline are applications of percent decrease.

To solve problems of this type, we use the following form of the percent equation.

percent change

amount of change

base

xL16.2

x=41.2 1 0.393)

39.3%=0.393

x

41.2

=0.393

x=

SECTION 2.2 Formulas and Percent 61

Interpreting Percents from a Graph

In 2007, Americans spent about $41.2 billion on their pets. Use the graph in FIGURE 3

to determine how much of this amount was spent on pet food.

NOW TRY EXAMPLE 7

EXERCISE 7
Refer to FIGURE 3. How much
was spent on vet care? Round
your answer to the nearest
tenth of a billion dollars.

NOW TRY ANSWER

7. $10.1 billion

Source: American Pet Products Manufacturers

Association Inc.

Spending on Kitty and Rover

Supplies/

medicine

23.8%

Live animal

purchases

5.1%

Grooming/boarding

7.3% Vet care

24.5%

Food

39.3%

FIGURE 3

Pythagoras

Subtract to

find this.

Solving Problems about Percent Increase or Decrease

(a)An electronics store marked up a laptop computer from their cost of $1200 to a

selling price of $1464. What was the percent markup?

“Markup” is a name for an increase. Let the percent increase (as a decimal).

Substitute the given values.

x= 0.22,or22% Use a calculator.

x=

264

1200

x=

1464 - 1200

1200

percent increase=

amount of increase

base

x=

EXAMPLE 8

Use the original

cost.

Subtract to find the

amountof increase.

The computer was marked up 22%.