Author note — to cover

Cover simple interest, named in R9's financial mathematics: the same interest on the principal every year, total interest and final balance after n years, and finding the rate, time or principal from a stated total. Contrast with compounding stays brief here; simple-versus-compound-interest and Growth and decay own it. Both tiers. (R9)

• Fluency — direct questions on simple interest, 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).