Remember that the third side — which is equal to 3√2 — is the circle's diameter. We're trying to find circumference, which, as stated earlier, is equal to pi times diameter (c = πd).

Example Calculate the circumference of the dartboard. The diameter is twice the radius. d = 20 × 2 = 40 cm Circumference = 40 × π = 125.7 cm (1 decimal place).

The circumference of a circle is calculated using the formula: circumference = π × diameter For any circle: circumference ÷ diameter = 3.1412 This number is Pi (π).