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Geometry & MeasuresKey Facts

The Two Essential Formulas

Part of Circumference & Area of Circles — GCSE Mathematics

This key facts covers The Two Essential Formulas within Circumference & Area of Circles for GCSE Mathematics. Revise Circumference & Area of Circles in Geometry & Measures for GCSE Mathematics with 11 exam-style questions and 7 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 3 of 9 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.

Topic position

Section 3 of 9

Practice

11 questions

Recall

7 flashcards

The Two Essential Formulas

Circumference

C = πd

or C = 2πr

Area

A = πr²

pi × radius × radius

⚠️ Area uses radius SQUARED! This is the most common mistake.

Keep building this topic

Read this section alongside the surrounding pages in Circumference & Area of Circles. That gives you the full topic sequence instead of a single isolated revision point.

Key VocabularyMethod: Finding CircumferenceThe Most Famous Number in MathsMethod: Finding Area

Practice Questions for Circumference & Area of Circles

A circle has radius r. Which pair of formulas gives the correct circumference C and area A?

  • A. C = πr², A = 2πr
  • B. C = 2πr, A = πr²
  • C. C = πd², A = πr
  • D. C = 2πr², A = πr
1 markfoundation

Explain why the circumference of a circle is measured in cm (or other length units) but the area is measured in cm² (square units).

2 markshigher

Quick Recall Flashcards

Circumference
C = πd or C = 2πr
Area of Circle
A = πr²

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Method: Finding Circumference