Is It A Prime Number, Yes or No? Jonathan Brinkerhoff

There are different kinds of numbers. You know about whole numbers, like 5, and fractions like ⅓. You know about odd and even numbers. Today, we’ll learn about another kind of number – prime numbers.

I’m going to show you some numbers. Some are prime and some are not. When you think you know what makes a number prime or not, raise your hand.

3 is a prime number 3 = 1 X 3

4 is not a prime number 4 = 1 X 4 4 = 2 X 2

5 is a prime number 5 = 1 X 5

6 is not a prime number 6 = 1 X 6 6 = 2 X 3

7 is a prime number 7 = 1 X 7

12 is not a prime number 12 = 1 X = 2 X 6 12 = 3 X 4

13 is a prime number 13 = 1 X 13

15 is not a prime number 15 = 1 X = 3 X 5

What do you think a prime number is?

You figured out that a prime number has only two factors, itself and 1.

Let’s Practice! If it’s a prime number If it’s not a prime number

8

9

14

17

21

10

19

You can correctly identify prime numbers.

2 is a prime number 2 = 1 X 2

9 is not a prime number 9 = 1 X 9 9 = 3 X 3

11 is a prime number 11 = 1 X 11

14 is not a prime number 14 = 1 X = 2 X 7

What do you think a prime number is?