Author note — to cover

Perimeter of rectilinear and straight-sided shapes, deducing the unmarked sides of L-shapes before adding, with simple algebraic perimeters included. Circles enter at Circumference of a circle, and shapes with curved edges at Semicircles and quarter circles; keep perimeter distinct from area throughout. Both tiers. (G17)

• Fluency — direct questions on perimeter, 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).