Question: what is the greatest common factor of 60 and 90 using prime factorization?
Answer: The prime factorization of 90 is: 2 x 3 x 3 x 5. The prime factors and multiplicities 60 and 90 have in common are: 2 x 3 x 5. 2 x 3 x 5 is the gcf of 60 and 90. gcf(60,90) = 30.