6th Grade · The Number System
Greatest Common Factor
6.NS.B.4
Definition
The largest factor that two or more numbers have in common.
Examples
- Factors of 12: 1,2,3,4,6,12. Factors of 18: 1,2,3,6,9,18. GCF = 6.
- The common factors of 12 and 18 are 1, 2, 3, 6 — the greatest is 6.
Key rule
Find all common factors, then pick the greatest.
Memory hook
The biggest factor they both share.