Unit 31: Algebraic Expressions and Variables

Day 25 of 30

Perimeter and area formulas as expressions

6-8Mathematics

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Learning Objective

Students will explore perimeter and area formulas as expressions through guided practice and application.

Today's Lesson

In this lesson, we'll explore perimeter and area formulas as expressions. Mathematical thinking develops logical reasoning and problem-solving abilities.

An expression is a combination of numbers, variables, and operations (like +, −, ×, ÷). Unlike an equation, an expression doesn't have an equals sign. Examples: 3x + 5, 2(4 + 1), or 7 − 2. Expressions represent a value, and we can simplify them by following the order of operations. Think of expressions as mathematical phrases, while equations are complete sentences!

As you work through today's material, pay attention to the examples and try to identify the patterns or strategies being used. This will help you apply these concepts to new problems.

Take notes on key points and make connections to what you've already learned in previous lessons.

Key Terms
Perimeter

The total length of a polygon's boundary

Area

The amount of surface enclosed within a boundary

Activities
Instructions
1. Review the example problems for perimeter and area formulas as expressions. 2. Identify the steps and strategies used. 3. Work through practice problems independently. 4. Compare solutions with a partner.
Materials Needed
  • Notebook
  • Calculator (if needed)
  • Graph paper
Practice Problems
1

A rectangle has length 8 cm and width 5 cm. What is its perimeter?

Hint: Add all four sides: 8 + 5 + 8 + 5
2

A square has sides of 4 inches. What is its perimeter?

Hint: All four sides are equal.
3

Find the perimeter: Triangle with sides 3 ft, 4 ft, 5 ft.

Hint: Add all three sides.

Teaching Tip

For advanced learners: Encourage deeper analysis and real-world connections. Consider extension activities that allow students to apply perimeter and area formulas as expressions to novel situations.

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