7th Grade Math

CELL PHONES A survey found that 25% of people aged 18–24 gave

up their home phone and only use a cell phone. If 3,264 people

only use a cell phone, how many people were surveyed?

Words

Variable

Equation

3,264 people is 25% of what number of people?

Let n represent the number of people.

3,264 = 0.25 · n

3,264 = 0.25 · n Write the percent equation. 25% = 0.25

_3,264

0.25 =

_0.25n

0.25 Divide each side by 0.25. Use a calculator.

13,056=n Simplify.

About 13,056 people were surveyed.

k. POPULATION The Miami-Dade County metropolitan area contains

13.3% of the population of Florida. If the population of Florida

is about 18,089,888 people, what is the population of the Miami-

Dade County metropolitan area?

Types of Percent Problems

Type Example Equation

Find the Percent 3 is what percent of 6?^3 =^ n ·^6

Find the Part What number is 50% of 6? p = 0.5 · 6

Find the Whole 3 is 50% of what number?^3 =^ 0.5 · w

Real-World Link

In the United States,

Anchorage, Alaska,

has the highest

percent of cell phone

users.

RR

Write an equation for each problem. Then solve. Round to the nearest

tenth if necessary.

Examples 1–3

1. What number is 88% of 300? 2. What number is 12% of 250?
   33 75 is what percent of 150? 4. 24 is what percent of 120?


2. 3 is 12% of what number? 6. 84 is 60% of what number?

Example 4 7. BUSINESS A local bakery sold 60 loaves of bread in one day. If 65% of

these were sold in the afternoon, how many loaves were sold in the

afternoon?

Lesson 2C Proportions and Equations 339

331_341_C06_L2_895130.indd 339 12/30/09 4:05 PM