Finding the greatest common divisor

1. Find the prime factorization for each number
2. Create a list of prime factors that are common to all numbers
3. The GCF is the product of the numbers on the list
4. Optional - it can be helpful to organize information in a table format

Example

• 40 and 60
• 40 = 2 x 2 x 2 x 5
• 60 = 2 x 2 x 3 x 5
• In common = 5 and two of the 2s (discard the unmatched 2)
• 2 x 2 x 5 = GCF 20