1. Variables and Patterns
Rules and Equations
Investigation 3

2. Equations with One Operation
3.1 Writing Equations
Equations with One Operation
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Rule Tells you how to find the value of a variable (usually written in words).
Equation A rule containing variables that represent mathematical relationships.
Ex: The cost in dollars is equal to 21 times the number of people. (Rule)
C = ● p (Equation)
C = 21●p
How much will it cost for 20 people?
C = 21●p
C = 21 ● 20
C = $420

3. 3.2 Writing More Equations
Equations with Two Operations
Steps in Writing Equations
Create a rule.
Develop an equation from the rule.
Example: A cell phone plan costs $5.00 for monthly access and .10 cents per minute. Write an equation. How much will it cost if you used 50 minutes?
A cell phone plan costs $5.00 for monthly access and .10 cents per minute (Rule)
C = $ m (Equation)
C=$ m

4. 3.3 Paying Bills and Counting Profits
Equations for Revenue, Expenses, and Profit
Steps for writing a rule from a chart
Look for a pattern of increase or decrease and how it relates.
Create the rule.
Make the equation.
Profit = Income – Expenses
Camp Income and Costs
Number of Campers
Income
Food
Class Materials 1
335 50 35 2
670
100 70
Income: Pattern – it increases by 335 per camper.
The income increases by 335 per camper. (Rule)
I = c (Equation)
I=335c