7th Grade Math

Get ConnectED

Proportions and Equations

PART A B C DE









.JMMJQFEFT
BOE

$FOUJQFEFT

$SVTUBDFBOT

4QJEFST

*OTFDUT

Arthropods

Multi-Part

Lesson 2

GLE 0706.2.4

Use ratios, rates and

percents to solve single-

and multi-step problems

in various contexts. Also

addresses GLE 0706.1.2.

Main Idea

Solve problems by

using the percent

equation.

Vocabulary

percent equation

The Percent Equation

ARTHROPODS Suppose there are

854,000 different species of spiders,

insects, crustaceans, millipedes,

and centipedes on Earth. The

graph shows that 88% of the

total number of species of

arthropods are insects.

1. Use the percent
   proportion to find how
   many species are insects.


2. Express the percent of
   insects as a decimal. Then
   multiply the decimal by 854,000.
   What do you notice?

You have used a percent proportion to find the missing part, percent,

or whole. You can also use a percent equation.

part

_

whole

= percent The percent must be written as a decimal or fraction.

part

_

whole

· whole = percent · whole Multiply each side by the whole.

part = percent · whole This form is called the

percent equation.

Find the Part

What number is 12% of 150?

Estimate 12% of 150 ≈ 0.1 · 150 or 15

part = percent · whole

p = 0.12 · 150 Write the percent equation. 12% = 0.12

p = 18 Multiply.

So, 18 is 12% of 150.

Write an equation for each problem. Then solve.

a. What is 6% of 200? b. Find 72% of 50.

Percent Equation Percent Equation

A percent must always be

converted to a decimal or

a fraction when it is used

in an equation.

V

p

Lesson 2C Proportions and Equations 337

331_341_C06_L2_895130.indd 337 12/30/09 4:05 PM