Author note — to cover

Cover exponential decay: repeated multiplication by a factor below 1 for radioactivity-style, medicine-dose and cooling contexts, halving as x0.5 per period, and why values approach zero without reaching it. Keep half-life language informal. Threshold questions belong to finding-how-long; the decay curve is sketch-recognition only, with plotting in Algebra at Higher. Both tiers. (R16)

• Fluency — direct questions on exponential decay, 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).