Question: what is the greatest common factor of 45 and 75 using prime factorization?
Answer: The prime factorization of 75 is: 3 x 5 x 5. The prime factors and multiplicities 45 and 75 have in common are: 3 x 5. 3 x 5 is the gcf of 45 and 75. gcf(45,75) = 15.