1777 One day, Mr. Buffon, a French natural philosopher, invited a room full of guests to do an interesting experiment to relieve boredom. I saw 70-year-old Mr. Buffon happily take out a piece of white paper, which was covered with parallel lines with equal distances. Then he grabbed a small needle and said to everyone, "Please throw these needles on the paper one by one, and wonderful things will happen naturally." The guest didn't know what medicine he was selling in the gourd, so he curiously threw the small needles on the paper one by one. Buffon has been counting. When the small needle is thrown away, put it away before throwing it away. Finally, Buffon announced the result: everybody threw the needle 22 12, number 3. 142. He smiled and said, "This is an approximate value of pi." So this is the famous "needle throwing experiment" in the history of mathematics. The probability of a gambler winning or losing is a mathematical model of classical probability. Here is a typical example of geometric probability. Generally speaking, if the distance between parallel lines is a, the needle length is l(l is less than a), the number of throws is n, and the number of times of intersecting with a straight line is n, then pi = 2ln/an. In the above experiment, the length of the small needle used by Buffon is exactly half of the distance between parallel lines, so the formula can be abbreviated as N/N.

Later, many people calculated the values according to the method created by Buffon. Among them, 190 1 year, the Italian Racharini released the needle 3408 times, intersecting 1808 times, and the best result was 6 digits accurate decimal 3. 14 15929.