Concept

Prime number:

A whole number greater than 1 whose only factors are 1 and itself.

Composite number:

A whole number greater than 1 that has at least one factor other than 1 and itself.

Rule

To figure out if a number is prime or composite:

1. Find all the factors of the number.
2. If the number has only two factors, 1 and itself, then it is prime.
3. If the number has more than two factors, then it is composite.

Example

Is the number 125 a prime number or a composite number?

Solution

To figure out if 125 is prime or composite:

1. Find all the factors of 125.
   1 x 125 = 125
   5 x 25 = 125
   25 x 5 = 125
   125 x 1 = 125
2. If the number has only two factors, 1 and itself, then it is prime.
   125 has four factors: 1, 5, 25, and 125
   125 is not a prime number

Since 125 is not a prime number, then it is a composite number.

Pre-requisite Skills

Multiplication facts (Grade 3 units 4 & 5)

Identify Factors (5.10.1)