You can list them.
The factors of 36 are:
1, 2, 3, 4, 6, 9, 12, 18, 36
The factors of 42 are:
1, 2, 3, 6, 7, 14, 21, 42
The common factors are:
1, 2, 3, 6
The Greatest Common Factor:
GCF = 6
you use prime factorization
you use a factor tree
you multiply them together
To find the greatest common factor (GCF) of two factors, first list the factors of each number. Then, identify the common factors between them. The GCF is the largest of these common factors. Alternatively, you can use the prime factorization method, where you break down each number into its prime factors and multiply the lowest powers of all common prime factors.
There cannot be a greatest common factor (GCF) of just one number. To be common there need to be at least two numbers. If you find all the factors of two or more numbers, and you find some factors are the same ("common"), then the largest of those common factors is the Greatest Common Factor.
Find out about factors and factor trees.
use common factors calculator
a and b have no common prime factors. Their LCM is their product.
Factors are useful when you're trying to reduce fractions. Multiples are useful when you're trying to find a least common denominator.
The factors of 100 are included in the factors of 200, but I did not use one to find the other.
turn the sentence into a question
One number can not have a common factor so there is NO GCF.. you need at least 2 You would use common factors for fractions, so to find the GCF you need 2 factors. (Assuming 1 and 28 here, it would be 28)