Question: what is the greatest common factor of 30 and 42 using prime factorization?
Answer: The prime factorization of 42 is: 2 x 3 x 7. The prime factors and multiplicities 30 and 42 have in common are: 2 x 3. 2 x 3 is the gcf of 30 and 42. gcf(30,42) = 6.