# Multiples and Common Factors of Numbers

Multiples and Common Factors of Numbers

1. Multiples of the Commonwealth of Two Numbers

Multiples of 3 are 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36, 39, …. Multiples of 4 are 4, 8, 12, 16, 20, 24, 28, 32, 36, 40, ….

The common multiples of 3 and 4 are 12, 24, 36,...

Let's find the common multiples of 4 and 5

Answer: The multiples of 4 are 4, 8, 12, 16, 20, 24, 28, 32, 36, 40, ….

The multiples of 5 are 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, …

So the common multiples of 4 and 5 are 20, 40, 60, ...

2. Common Factors of Two Numbers

The following is an example of the common factors of two numbers.

a. The factors of 8 are 1, 2, 4, 8.

The factors of 12 are 1, 2, 3, 4, 6, 12.

The common factors of 8 and 12 are called the common factors of 8 and 12.

So the common factors of 8 and 12 are 1, 2, 4.

b. The factors of 16 are 1, 2, 4, 8, 16.

The factors of 18 are 1, 2, 3, 6, 9, 18.

So the common factors of 16 and 18 are 1.2.

3. Prime Numbers

A prime number is a number that has exactly two factors.

Look at the factors of the following numbers!

- The factors of 2 are 1 and 2. So 2 is a prime number.

- The factors of 3 are 1 and 3. So 3 is a prime number.

- The factors of 5 are 1 and 5.

So 5 is a prime number.

Number 1 is not a prime number because number 1 only has one factor, which is number 1 itself. The number 2 is the only even prime number.