Lesson objective: Use an area model to determine if a number is prime or composite.

This lesson helps to build procedural skill with determining if a number is prime or composite. An area model is used here because it connects students' knowledge of multiplication and factor pairs to the new concept of prime and composite numbers. This work develops students' understanding that a prime number is a whole number greater than one that has only one factor pair and that a composite number is a whole number greater than one that has more than one factor pair.

Students engage in Mathematical Practice 3 (construct viable arguments) as they create area models to justify their conclusions on prime and composite numbers.

**Key vocabulary:**

- area model
- composite
- factor pair
- prime

**Special materials needed:**