GCSE Maths (AQA)

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Circumference from Radius

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Geometry and Measures Mensuration and Calculation

Circumference from Radius

2:15 Circumference of a Circle
Spec G17
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  • The formula for the circumference of a circle can be written as C = 2��R
  • The circumference of any circle is equal to its diameter multiplied by pi (��)
  • The formula for the circumference of a circle in terms of the radius is C = ��D
  • The diameter is twice the length of the radius (D = 2R)
  • To calculate the radius of a circle, rearrange the equation for circumference to make the radius the subject: R = C / 2��
  • Plug in the given values to calculate the radius
  • The radius can be calculated as R = 5 / (2��), which equals 0.796 meters to 3 significant figures (3SF)

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