Question: what is the highest common factor for 50 and 90?
Answer: The prime factorization of 50 is: 2 x 5 x 5.
The prime factorization of 90 is: 2 x 3 x 3 x 5.
The prime factors and multiplicities 50 and 90 have in common are: 2 x 5.
2 x 5 is the gcf of 50 and 90.
gcf(50,90) = 10.