The Greatest Common Factor (GCF) is the largest number that divides exactly into two or more numbers. It’s useful for simplifying fractions and solving real-world problems.
How to Find the GCF
List all the factors of each number.
Circle the ones they have in common.
The greatest one they share is the GCF.
Example
Factors of 12: 1, 2, 3, 4, 6, 12
Factors of 16: 1, 2, 4, 8, 16
Common factors: 1, 2, 4 ? Greatest: 4
Other Methods
You can also use prime factorization to find the GCF.
Find the product of all prime factors they have in common.