Drop the needles on the paper and calculate the percentage that fall on a line. With enough attempts, the answer should be the needle length divided by the width between lines, all multiplied by 2/pi.

将针随便丢在纸上，然后计算出落在线上的针的百分比，随着尝试次数的足够多，最终这个百分比将越来越逼近针的长度除以格子的宽度再乘以2/pi。