1. Complete the diagonal factor tree
Check the factor tree
Each split must multiply back to the number above it. The left branch should be the smallest prime factor.
2. List the prime factors
Write the prime numbers from the ends of the branches.
3. Build the missing factors
Use the prime factors to make products. Start with the longest product, then try shorter products, then check the tree for anything missing.
4. List every factor
Use 1, the prime factors, the products above, and the factor tree to check what is missing.