what are the common factors of 12

You can find common factors by comparing the factors of 2 different numbers, like 12 and 20. You can determine common factors in 2 way: either making a list of the factors of both numbers or by finding the prime factors of both of them. Both methods are useful, but for smaller numbers, memorizing the multiplication/division facts really helps in factoring.

OK, here are the factors of 12: 1 x 12, 2 x 6, 3 x 4 and put in order: 1, 2, 3, 4, 6, 12

If you were finding the common factors of 12 with 20, then you would have to find the factors of 20 also:

1 x 20, 2 x 10, 4 x 5 and put in order: 1, 2, 4, 5, 10, 20

Are there numbers that are in both lists (common to both)? Yes, 1, 2, 4.

If you are looking for the GREATEST common factor, then you want the largest number that is in both lists: 4

I hope that helps in thinking about how factors can be common.

## Comments

common factors of 12 and ?