Topic summary · Foundation · CIE Core

Circles summary

Circle measures use $\pi$ : circumference $2\pi r$ or $\pi d$ , area $\pi r^2$ . Leave answers in terms of $\pi$ when asked.

Open Learning Sheet — Circles Download Circles answers PDF

Files: foundation-18 Circles handout.pdf · foundation-18 Circles handout answers.pdf · free public downloads · diagrams in the PDFs

Key learning points

Radius vs diameter: $d=2r$ .
Arc length and sector area are fractions of the full circle: $\frac{\theta}{360}$ .
Exact answers often keep $\pi$ ; decimal answers need the degree of accuracy stated.

Worked example 1 — Circumference

Radius $7$ . Circumference in terms of $\pi$ ?

Working

C=2\pi r=14\pi

$C=2\pi r$ .

Worked example 2 — Area

Radius $7$ . Area in terms of $\pi$ ?

Working

A=\pi r^2=49\pi

Square the radius first.

Worked example 3 — Arc length

Radius $6$ , angle $60^\circ$ . Arc length in terms of $\pi$ ?

Working

\ell=\tfrac{60}{360}\times2\pi\times6=2\pi

Fraction of the circumference.

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.

Open Learning Sheet Answers PDF

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