piis the ratio of what to what

Pi is the ratio of a circle’s circumference to its diameter.

Quick Scoop: What does that mean?

When you take any perfect circle, measure all the way around it (the circumference), then divide that by the distance straight across through the center (the diameter), you always get the same number: π, about 3.14159.

So in formula form, it’s:

• π=circumferencediameter\pi =\dfrac{\text{circumference}}{\text{diameter}}π=diametercircumference​

For example, if a circle has a diameter of 2 units, its circumference will be about 2×π≈6.283182\times \pi \approx 6.283182×π≈6.28318 units.

TL;DR: “pi is the ratio of what to what?” → the ratio of a circle’s circumference to its diameter.

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