Author note — to cover

The definition of prime, why 1 is excluded, identifying primes to 50, and testing numbers like 91, 97 and 117 by trial division by primes up to the square root. Prime factorisation lives on the next page; infinitude-of-primes proofs are A level. Both tiers. (N4)

• Fluency — direct questions on primes and testing for primality, 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).