How do you figure greatest common factor?

Answer 1

To find the greatest common factor (GCF), first find the prime factorization of the two numbers.

The GCF is the product of all of the prime factors the two numbers have in common.

If two numbers have no common factors, the GCF is 1. (Since all numbers are divisible by 1.)

Example: Find the GCF of 60 and 24.

Prime factors of 60: 2, 2, 3, 5

Prime factors of 24: 2, 2, 2, 3

Common factors: 2, 2, 3

GCF: 2x2x3=12

Example: Find the GCF of 17 and 21.

Prime factors of 17: 17

Prime factors of 21: 3, 7

Common factors: None (1).

GCF: 1

Answer 2

The concept of factors (and common factors) is applicable to whole numbers, not to fractions. The numerator and denominator of a rational fraction are integers and they can have a greatest common factor but that is not a factor of the fraction.

Answer 3

when the numbers are the same and you can't go any higher than that