Let us take some example to find the common factor

1. Find the common factor of 4 and 18

Factor of 4 = 1, 2, 4

Factor of 18 = 1, 2, 3, 6, 9, 18

Now the numbers 1, 2 are present in both the numbers.

So the numbers 1, 2 are the common factor of numbers 4 and 18

2. Find the common factor of 5 and 18

Factor of 5 = 1, 5

Factor of 18 = 1, 2, 3, 6, 9, 18

Now only the number 1 is present in both the numbers.

So the number 1 is the common factor of numbers 5 and 18

3. Find the common factor of 3, 12 and 18

Factor of 3 = 1, 3

Factor of 12 = 1, 2, 3, 4, 6, 12

Factor of 18 = 1, 2, 3, 6, 9, 18

Now the numbers 1, 3 are present in both the numbers.

So the numbers 1, 3 are the common factor of numbers 3, 12 and 18

In this way, we can find the common number between the numbers.