Author note — to cover

HCF of two numbers beyond 100 from index-form prime factorisations, taking each shared prime to its lower index; what HCF means; listing method as backup for small numbers. LCM is the sibling page; three numbers and Venn diagrams live on hcf-lcm-venn. Both tiers. (N4)

• Fluency — direct questions on highest common factor, limited to this lesson's stated scope (4 questions).
• Application — use the same skill in unfamiliar or contextual questions without introducing a later method (4 questions).
• Check — questions built around the exclusions and likely misconceptions named in the lesson brief (4 questions).