Finding the greatest common factor (GCF) of a set of numbers is easy, but you need to know how to do it. To find the greatest common factor of two numbers, you need to know how to factor the two numbers. To do so, you need to know your schedule.
Step
Method 1 of 2: Comparing the Same Factors
Step 1. Find the factors of the numbers
You don't have to know the prime factorization to find the greatest common factor. Start by finding all the factors of the numbers you are comparing.
Step 2. Compare the factor sets until you find the largest number in both factors
Method 2 of 2: Using Prime Numbers
Step 1. Factor out each number by its prime numbers
A prime number is a number greater than 1 that has no factors except itself. Examples of prime numbers are 5, 17, 97, and 331, to give some examples.
Step 2. Identify any prime factors that are common
Choose any prime number that is the same in both factors. There may be several factors in common.
Step 3. Calculate:
If only one prime factor is the same, then that number is your common factor. If multiple prime factors are the same, then multiply all the prime factors together to get your greatest common factor.
Step 4. Study this example
To apply this method, study this example.
Tips
- A prime number is a number that can only be divided by one and itself.
- Did you know that the mathematician Euclid in the third century B. C. E invented an algorithm to find the greatest common factor in the case of two natural numbers or two polynomials?
