Find the greatest common factor of 15 and 42

3 is the greatest common factor of 15 and 42 is the correct answer.

First you had to find the prime factorization of 15: 1, 3, 5, 15. And then, you had to find the prime factorization of 42: 1, 2, 3, 6, 7, 42. You can also to used their factor of 15: . And then you can also to used their factor of 42: . And it gave us the final answer is 3 is the greatest common factor of 15 and 42. Hope this helps! And thank you for posting your question at here on , and have a great day. -Charlie