Common factors are numbers that divide evenly into two or more numbers. The Greatest Common Factor (GCF), also called the Greatest Common Divisor (GCD), is the largest number that divides evenly into both numbers.

Example:

For numbers 12 and 18:

• Factors of 12: 1, 2, 3, 4, 6, 12
• Factors of 18: 1, 2, 3, 6, 9, 18
• Common factors: 1, 2, 3, 6
• Greatest Common Factor: 6

Uses of GCF:

• Simplifying fractions
• Finding equivalent ratios
• Solving problems involving equal groups