Lesson 9

Perimeter Problems

Lesson Purpose

The purpose of this lesson is for students to find unknown side lengths given the perimeter of a shape and solve problems involving perimeter.

Lesson Narrative

In previous lessons, students learned how to find the perimeter of shapes given all sides lengths or some side lengths. In this lesson, students use their understanding of perimeter to find missing side lengths when given the perimeter. Then, students solve problems in situations that involve perimeter. This lesson prepares students to think carefully about the difference between perimeter and area, which will be addressed in subsequent lessons.

  • Engagement
  • MLR8

Learning Goals

Teacher Facing

  • Find unknown side lengths given the perimeter of a shape.
  • Solve problems that involve perimeters of shapes.

Student Facing

  • Let’s solve problems about perimeter.

Required Preparation

CCSS Standards


Lesson Timeline

Warm-up 10 min
Activity 1 15 min
Activity 2 20 min
Lesson Synthesis 10 min
Cool-down 5 min

Teacher Reflection Questions

How are students working toward multiplication and division fluency while solving perimeter problems?

Suggested Centers

  • Can You Draw It? (1–5), Stage 3: Grade 3 Shapes (Addressing)
  • Which One? (K–5), Stage 4: Grade 3 Shapes (Addressing)
  • How Are They the Same? (1–5), Stage 3: Grade 3 Shapes (Addressing)

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