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# Pi and the circumference of a circle

### See also

Pi is the ratio of the circumference of a circle to its diameter, or π = C/d. From this formula we then get the formula C = π*d*.

I go through practice problems where we calculate the circumference, given either the diameter or the radius, and then a problem where we are asked the radius, given the circumference. Lastly, we look at at real-life problem that involves the length of a path in a garden.

How to calculate the area of a circle, plus simple proof for the formula — video lesson

Math Mammoth Geometry 2 — a self-teaching worktext with explanations & exercises (grades 4-5)

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