7th Grade Math

Addition and Subtraction Equations

PART A B CD

Multi-Part

Lesson 1

Get ConnectED

GLE 0706.3.7

Use mathematical models

involving linear equations

to analyze real-world

phenomena. GLE 0706.3.8

Use a variety of strategies to

efficiently solve linear

equations and inequalities.

Also addresses GLE 0706.1.4,

GLE 0706.1.8, SPI 0706.3.7.

Solve Addition and Subtraction

Equations with Bar Diagrams

CELL PHONES In a recent year, 15 of the 50 states had a law banning

the use of handheld cell phones while driving a school bus. How

many states did not have this law?

What do you need to find? how many states did not have a cell

phone law for school bus drivers

You can represent this situation with an equation.

Draw a bar diagram that represents the total number of

states and how many have passed a law.

Write an equation from the bar diagram. Let x represent

the states that do not have a cell phone law for school

bus drivers.

15 + x = 50

Use the work backward strategy to solve the equation.

Since 15 + x = 50, x = 50 - 15. So, x = 35.

Check 15 + 35 = 50 

So, 35 states did not have a law banning the use of cell phones

by bus drivers.

the Results

1. Suppose nine more states adopt similar laws. How would the
   equation change?


2. How would the diagram change if the U.S. Virgin Islands and
   Puerto Rico were counted with the United States?

Main Idea

Write and solve

addition and

subtraction

equations using

bar diagrams.

204 Equations and Inequalities

50 states

15?

states with a law states that do not have a law

204_213_C04L1_895130.indd 204 12/31/09 3:55 PM