What is the gcf of 40 and 60 and 80?

Answer 1

The gcf is the greatest common factor. A way of finding the gcf of three numbers is to find the gcf of the first two and then finding the gcf of that number and the third number. Because of the unique prime factorization theorem, the greatest common factor will be a product of some of the prime factors in either number. The prime factorization of 40 is 2^3 * 5 and the prime factorization of 60 is 2^2 * 3 * 5, so the gcf is going to be what is in both, or, in this case, 2^2 * 5. Th prime factorization of 80 is 2^4 * 5 and so gcf of all three numbers is 2^2 * 5, or 20.