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 + 20 n – 20 20 ÷ 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

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

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?

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.

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.

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?

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.