How do you determine if a number is a prime or composite number?

For example:Is 15 a prime or composite number?

You will learn how to determine if a number is prime or

composite number by using area models.

Let’s Review

2x 3

=x 2

3

Multiplication can be shown as an area model.

A Common Mistake

Not all odd numbers are prime numbers.

5 is ODD & a prime

9 is ODD & is NOT prime

Core Lesson

A prime number has ONLY one set of factor pairs (1 and itself).

5:

1x5

9:

1x9

3x3

prime composite

Core Lesson

Is 15 a prime or composite number?

15: 1 x 15

3 x 5

In this lesson you have learned how to determine if a number is prime or composite by using

area models.

Guided Practice

17Prime or Composite?

1 x 17= 17

Extension Activities

Look at these numbers: 10, 11, and 12

Which ones are prime?

Which ones are composite?

Extension Activities

Is 81 a prime or composite number? How do you know?

Extension Activities

What other strategies can you use to find out if a number is prime or composite?

Extension Activities

Can a multiple of a number be a prime number? Explain your thinking.

Quick Quiz

16: Prime number or Composite number?

Find all the factor pairs for 13. Then decide if it is a prime or composite number.