1. 1-3 Writing Algebraic Expressions Part 1 – Example Writing Algebraic Expressions from Words
You have described a real world situation using words or symbols. You can also write algebraic expressions to represent real world situations that have unknown value.
Use the following operations and algebraic expressions to complete the table.
subtraction addition n n – ÷ n
Word Phrase
Operation
Algebraic Expression
a number plus 20
20 times a number
multiplication
20n
the difference of a number and 20
20 divided by a number
division

2. Part 1 – Example Writing Algebraic Expressions from Words Solution
Word Phrase
Operation
Algebraic Expression
a number plus 20
addition
n + 20
20 times a number
multiplication
20n
the difference of a number and 20
subtraction
n - 20
20 divided by a number
division
20 ÷ n

3. Part 2 – Example Representing Real-World Situations Using Algebraic Expressions with One Operation
When writing algebraic expressions, you can choose any letter
to represent an unknown quantity.
A state park has 3 lakes. In the spring,
each lake was stocked with the same
number of fish. What algebraic expression
represents the total number of fish in the
lakes?

4. Part 2 – Example Representing Real-World Situations Using Algebraic Expressions with One Operation Solution
Let f represent the number of fish in one lake. Then
write the expression.
3 x f, or 3f
The expression 3f, where f is the number of
fish in one lake, represents the number of
fish in all lakes.

5. Part 3 – Example Using Graphic Organizers to Write Algebraic Expressions
The Know-Need-Plan graphic organizer is a tool that can help you in making sense of problems.
Suppose a store that personalizes t-shirts charges $15 for a shirt plus $2 for each letter. What algebraic expression can be used to represent the total cost of a shirt with n letters?
Know
The cost of a
t-shirt: $15
The cost for one letter: $2
Need
An algebraic expression to represent the total
cost of a t-shirt
with n letters.
Plan
Define what the variable represents.
Write an algebraic expression.

6. Part 3 – Example Using Graphic Organizers to Write Algebraic Expressions
A national park charges $25 per bus and $12 per person for
an organized tour group. What algebraic expression can be
to represent the total cost for a one-day tour with one bus
and n people?

7. Part 3 – Example Using Graphic Organizers to Write Algebraic Expressions Solution
Know
The admission fee per bus: $25
The admission fee per person: $12
Need
An algebraic expression to represent the total admission cost for the group
Plan
Define what the variable represents.
Write an algebraic expression.
Define what the variable represents. Let n = number of people.
Write an algebraic expression.
12 x n + 25
The expression 12n + 25 represents the total admission cost for the
tour group.