Accuracy summary

Key learning points

• If $x$ is given to nearest unit $u$, error is $\pm\tfrac12 u$.
• Lower/upper bounds feed into calculations for maximum/minimum results.
• Choose sensible accuracy for the context (money → 2 d.p., etc.).

Worked example 1 — Bounds

A length is $12.4\,\mathrm{cm}$ to 1 d.p. Find the error interval.

Working

Half a unit in the last digit.

Worked example 2 — Upper bound calculation

Sides $4.2$ and $3.1$ (1 d.p.). Upper bound of rectangle perimeter?

Working

Use upper bounds of both sides.

Worked example 3 — Truncation

Truncate $3.89$ to 1 d.p.

Working

Truncation cuts digits; rounding would give $3.9$.

Scaffolded Learning Sheet and answers (PDFs)

This page is a short, searchable overview for revision and search engines. Use the Scaffolded Learning Sheet first, then the Answers PDF for a full written solution. The printable PDFs remain the main classroom resource.