Author note — to cover

Writing the error interval of a value rounded to a place value or decimal places, half a unit either side with strict inequality on top, e.g. 5.65 at-most x < 5.75; N15 names inequality notation for these intervals. Truncation and significant-figure versions get sibling pages. Both tiers. (N15)

• Fluency — direct questions on error intervals from rounding, 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).