Here’s a simple question with a simple answer.
From grade 6 you know:
c = pi*d
But where the did they get this number pi?
pi = c / d
It comes from experiment.
A teacher once told me that the way we know anything at all about our world is by experiment. All science comes from experiment. We experiment, then we form theories to explain the results we got from experimentation.
So here’s an experiment to explain pi:
Take any DVD and use a tape measure to measure its circumference.
Then measure the diameter of that DVD (width across its widest part).
circumference = 38cm
diameter = 12cm
Then, use a calculator and divide.
pi = 38/12 = 3.166666 . . . close enough to 3.14159 —
And that’s the origin of PI. It comes from any circle, anywhere in the universe that is perfectly round.