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# Factors And Divisibility

## Factors

We saw factors in the earlier pages where we were looking at prime numbers. There we saw how the numbers that you multiply together to get another number are called factors. So if we were looking for the factors of 15 we would get (1,3,5,15).

## Divisibility

Divisibility is the word we use to say that some number can be divided by another number. So 10 is divisible by 2 because it is possible to divide 10 by 2 without getting a decimal number. One thing to note is that 2 is a factor of 10.

## Greatest common divisor

You may be asked for the greatest common divisor between 2 numbers. This means you take the largest factor that can be divided into both numbers. Example would be Find the greatest common divisor between 15 and 30. So first write out the factors of each number:

15 = {1,3,5,15}
30 = {1, 2, 3, 5, 6, 10, 15, 30}

So here we see that that these two numbers have a lot of similar factors they are {3,5,15}. So here 15 would be the greatest common divisor.