Lesson 3
Prime and Composite Numbers
Lesson Purpose
Lesson Narrative
In previous lessons, students were introduced to the terms “multiples” and “factor pairs.” In this lesson, they learn that whole numbers can be classified as prime or composite based on the number of factor pairs they have.
Students reason about these numbers in terms of the area and pairs of side lengths of rectangles. They learn that a prime number has exactly 1 factor pair—1 and the number itself, and that a composite number has more than 1 factor pair. They relate “prime” to a number that could represent the area of only one rectangle (with only one pair of side length) and “composite” to a number that could represent the area of multiple rectangles (with multiple pairs of side lengths).
Math Community
Tell students that, at the end of the lesson, they will be asked to identify specific actions they personally experienced from their “Doing Math” list (both teacher and student sections).
 Engagement
 MLR8
Learning Goals
Teacher Facing
 Determine whether a given whole number in the range 1–100 is prime or composite.
 Find the factor pairs of a given whole number 1–100.
Student Facing
 Let’s identify prime and composite numbers.
Required Materials
Required Preparation
Activity 1:

Create a set of cards from the blackline master for each group of 2.
Lesson Timeline
Warmup  10 min 
Activity 1  15 min 
Activity 2  20 min 
Lesson Synthesis  10 min 
Cooldown  5 min 
Teacher Reflection Questions
Suggested Centers
 Find the Number (4), Stage 1: Factors (Addressing)
 Five in a Row: Multiplication (3–5), Stage 1: Factors 1–5 and 10 (Supporting)
Print Formatted Materials
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Additional Resources
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