So what are the most factors that we can take from both 21 and 30 to make the largest possible numbers? Find the GCF of 6 and 4 using prime factorization.

Hide Ads About Ads. So the GCF of 6 and 4 is equal to 2.

So you could do it either way. These are all, we could say, divisors of 10.

So let me write that down. Example 1: I think I've got all of them.

Greatest Common Factor

So the greatest common factor of 10 and 7, or the greatest common divisor, is going to be equal to 1. And another example: And so 12 30 can be simplified to 2 5. Find the prime factorization of the two numbers. So the greatest common factor or greatest common divisor is going to be a product of these two.

Math - Examples of HCF By Prime Factorization - English

And now what are the common factors? To log in and use all the features of Khan Academy, please enable JavaScript in your browser.

Or you can break it down into its core constituencies, its prime factors, and then figure out what is the largest set of common prime factors, and the product of those is going to be your greatest common factor. 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 30.

Up Next. We want to think about what is our GCD of 10 and 7? Video transcript We're asked, what is the greatest common divisor of 20 and 40?

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Let's start with an Example... Or we can find the prime factors and combine the common ones together: Math Pre-algebra Factors and multiples Greatest common factor. So let's say these two numbers were not 21 and 30, but let's say we care about the greatest common divisor not of 21, but let's say of 105 and 30.