French mathematician named Georges Buffon devised a way to calculate pi based on probability. Buffon’s method begins with a uniform grid of parallel lines, a unit distance apart. If you drop a needle of length k < 1 on the grid, the probability that the needle falls across a line is 2k divided by pi. Thus the number of needles landing on the line divided by the total number of throws = 2k divided by pi. Knowing k we can now solve for pi. The more throws we make, the greater the accuracy.
Buffon casting needles on a hardwood floor
(the opening gambit of geometrical probability)
counting the number of times
the needle falls across the lines
working backwards to a solution of pi
(centuries of mathematicians later landing
on the cracks in his theory)