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Circumference of a Circle Flashcards
GCSE Mathematics (Edexcel) 1MA1
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Circumference of a circle
The distance around the edge of a circle.
Formula for circumference (using diameter)
Circumference = π × diameter (C = πd).
Formula for circumference (using radius)
Circumference = 2 × π × radius (C = 2πr).
Value of π (pi)
π is approximately 3.14159 or can be approximated as 3.14 in calculations.
Relationship between diameter and radius
Diameter = 2 × radius (d = 2r).
Units of circumference
Circumference is measured in the same units as the circle's radius or diameter (e.g., cm, m).
How to calculate diameter from circumference
Diameter = Circumference ÷ π (d = C ÷ π).
How to calculate radius from circumference
Radius = Circumference ÷ (2π) (r = C ÷ 2π).
Circumference of a circle with diameter 10 cm
Circumference = π × 10 = 31.4 cm (using π ≈ 3.14).
Circumference of a circle with radius 7 m
Circumference = 2 × π × 7 = 43.96 m (using π ≈ 3.14).
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