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
Addressing
Lesson Timeline
Warmup  10 min 
Activity 1  15 min 
Activity 2  20 min 
Lesson Synthesis  10 min 
Cooldown  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)
Print Formatted Materials
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Additional Resources
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