Let us review first some of the concepts that can help you understand Least Common Multiple (LCM). A. Find the Greatest Common Factor (GCF) of the given pair of numbers using any of the following methods: listing, prime factorization, and continuous division. 1. 18 and 54 4. 72 and 66 2. 21 and 56 5. 64 and 72 3. 81 and 99​