How can i get the gcf

So note down color red 3 and divide both numbers by 3 to get: 21 and Note that both 21 and 15 are divisible by 3 again.

So note down color red 3 and divide to get: 7 and 5. How do you find the greatest common factor GCF of two numbers? George C. Oct 16, Here are four methods Explanation: There are several methods. OK, there is also a really easy method: we can use the Greatest Common Factor Calculator to find it automatically. Example: Factors of 12 and 30 Factors of 12 are 1, 2, 3, 4, 6 and 12 Factors of 30 are 1, 2, 3, 5, 6, 10, 15 and It is a common factor when it is a factor of two or more numbers.

Example: The common factors of 15, 30 and Factors of 15 are 1, 3, 5, and 15 Factors of 30 are 1, 2, 3, 5, 6, 10, 15 and 30 Factors of are 1, 3, 5, 7, 15, 21, 35 and The factors that are common to all three numbers are 1, 3, 5 and 15 In other words, the common factors of 15, 30 and are 1, 3, 5 and The "Greatest Common Factor" is the largest of the common factors of two or more numbers. Tips and Warnings. Related Articles. Article Summary. Method 1. Find factors of the number. You don't have to know prime factorization to find the greatest common factor.

Start by finding all the factors of the set you are comparing. Compare the sets of factors until you find the biggest number that's in both sets. Method 2. Factor each number completely into its prime numbers. Examples of prime numbers include 5, 17, 97, and , to name just a few. Identify any common prime factors. There can be several common factors, one common factor, or none.

Calculate: If there are no common factors then the greatest common factor is 1. If there's only one prime common factor, then that's your common factor.

If there are multiple prime common factors, then multiply all the prime common factors together to get your greatest common factor.

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