Samantha K. answered 08/22/13
Licensed Elementary Teacher
So the problem has given you a list of numbers: 4, 6, 9, and 15 and you are to find the greatest common factor. First we know that a factor is found when something is multiplied. So the first thing we need to do is find what numbers can be multiplied to find the given list of numbers.
I'll start with 4. 1 x 4=4 and 2 x 2 = 4 so the factors here are 1,4, and 2.
Next, is 6. 1 x 6 and 2 x 3. The factors here are 1, 2, 3, and 6.
Then 9. 1 x 9 and 3 x 3. The factors here are 1, 3, and 9
Finally, 15. 1 x 15 and 3 x 5. The factors here are 1, 3, 5, and 15.
Now we go back to the factors we've found and find the largest that all of them have, 1 in this case.