Lesson plan

4. Determine prime and composite numbers (C)

teaches Common Core State Standards CCSS.Math.Content.4.OA.B.4 http://corestandards.org/Math/Content/4/OA/B/4
teaches Common Core State Standards CCSS.Math.Practice.MP3 http://corestandards.org/Math/Practice/MP3
teaches Common Core State Standards CCSS.Math.Practice.MP7 http://corestandards.org/Math/Practice/MP7

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Lesson objective: Understand that prime numbers are whole numbers greater than 1 that have only 2 factors. Understand that composite numbers are whole numbers greater than 1 with more than 2 factors.

Students bring prior knowledge of multiplication and division within 100 and factors and multiples from 3.OA.A.3 and 4.OA.B.4. This prior knowledge is extended to prime and composite numbers as students use area models and t-charts to determine if numbers are prime or composite. A conceptual challenge students may encounter is determining if odd numbers are prime or composite due to the common misconception that all odd numbers are prime.

The concept is developed through work with area models and t-charts, which are tools to determine factors of whole numbers.

This work helps students deepen their understanding of number because prime and composite are new ways to describe a number greater than one.

Students engage in Mathematical Practice 3 (construct viable arguments and critique the reasoning of others) as they demonstrate their thinking process and justify their conclusions about prime or composite numbers. Students will also need to analyze the reasoning and models of other students to determine if they correctly identified numbers as prime or composite.

Key vocabulary:

  • composite
  • prime

Special Materials:

  • counters or cubes (optional - for students who need to sort for equal rows and columns)