Algebraic Expressions

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# Algebraic Expressions - PowerPoint PPT Presentation

Algebraic Expressions. Everyday Math Lesson 10.3. Lesson Objectives. I can identify and use patterns in tables to solve problems I can write algebraic expressions to model rules I can use variables to write number models that describe situations. Mental Math. 4 + 7 30 + 70 50 + 60

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### Algebraic Expressions

Everyday Math Lesson 10.3

Lesson Objectives
• I can identify and use patterns in tables to solve problems
• I can write algebraic expressions to model rules
• I can use variables to write number models that describe situations
Mental Math

4 + 7 30 + 70 50 + 60

84 + 7 30 + 78 150 + 260

84 + 47 30 + 778 152 + 263

MathMessage( 3 minutes)

Joe and Maria are 5th graders. Joe is 2 inches taller than Maria. Make a table of 4 possible heights for Joe and Maria.

Math Message Follow-Up(5 minutes)
• How tall is Joe?
• What does his height depend upon?
• How tall is Maria?
Introducing Algebraic Expressions

* The table of Maria and Joe’s height is similar to a “What’s My Rule?” table.

• What was the rule for Maria and Joe’s table?
• Let’s represent Joe’s height using an algebraic expression. (“M” represents Maria’s height)

M + 2

M

M + 2

Turn to pg. 218 in your SRB.

• Study the examples of expressions that algebraic and those that are not.
• What’s the difference????
• Expressions use operation symbols (+, -, *, /) to combine numbers, but algebraic expressions combine variables and numbers.
• KEY POINTS:
• A situation can be represented in several ways (words, table, or symbols)
• Algebraic expressions use variables and other symbols to represent situations
• To evaluate an A.E means to substitute values for variables and solve.
Practice!Propose algebraic expressions to fit the situations
• Sue weighs 10 pounds less than Jamal. If J= Jamal’s weight, then J-10 represents Sue’s weight.
• Isaac collected twice as many cans as Alex. If A= the number of cans Alex collected, then 2 * A, (or 2A) represents the number of cans Isaac collected.
• There are half as many problems in today’s assignment as there were in yesterday’s. If Y= the number of problems in yesterday’s assignment, then there are ½ Y, ½ * Y, or Y/2 problems in today’s assignment.
Algebraic Equations
• Expressions can be combined with relation symbols (=, <, >) to make number sentences.
• X + 2 = 15
• 3y + 7 < 100

* These are called “Algebraic Equations” (number sentences that contain algebraic expressions)

Writing Algebraic Expressions
• Turn to pg. 341 & 342 in your journal.
• Let’s go over problem 1
• Complete the statements on both pages with a partner.
• When you are finished, complete the “What’s My Rule” on pg. 343.
Independent Work
• On your own at a level 0, complete Math boxes on page 344.
• When you are finished, you may work on Study Link 10.3