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 12
12 = 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 15
15 = 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 14
14 = 2 X 7
What do you think a prime number is?