Find the Greatest Common Factor By Prime Factorization #1

Find the greatest common factor of two numbers by finding the prime factorization with this helpful number theory worksheet! Designed for a fifth- and sixth-grade math curriculum, this one-page practice worksheet walks through an example of how to find the greatest common factor (GCF) by completing factor trees to identify what prime factors two numbers have in common and then multiplying those common prime factors. Learners will then use this method to find the greatest common factor in four different practice problems, all of which feature numbers under 100. For additional practice, check out Find the Greatest Common Factor by Prime Factorization #2 and Find the Greatest Common Factor by Prime Factorization #3.