What do the numbers mean in pi?

Answer 1

Pi is the word we use to define the ratio of the circumference of a circle to the diameter. The actual number is called an irrational number because it cannot be expressed exactly as a fraction. Nor can it be expressed exactly as a decimal so we use an approximation. The most often used approximations are 22/7, as a fraction, and 3.14 as a decimal. This is accurate enough for everyday use.

So using these numbers, if we know the diameter we can calculate the circumference, or if we know the circumference we can calculate the diameter.

(Incidentally it has many other uses too.)

For instance, if a circle has a diameter of 10 units (inches, centimetres, miles, any unit), then my multiplying this number by Pi we know the circumference is 3.14 times larger than the diameter or 31.4 of the same units. This also works in reverse, if we know the circle has a circumference of 10 units we divide by Pi to find the diameter.