72/(7-3)*3=54

In the history of mathematics, people have always attached great importance to the accuracy of pi, which has become a symbol to measure the development level of a country's mathematics. Throughout the calculation history of pi, its calculation methods can be roughly divided into geometric method, analytical method, experimental method and computer calculation method.

First, the geometric method Around 240 BC, Archimedes used the exhaustive method to find the value of π for the first time in his book The Measurement of Circle. The exhaustive method uses the perimeter of inscribed and circumscribed regular polygons to approximate the perimeter of a circle. He made a polygon with 96 sides, from which he got the value of π as follows.

The "trick" is to approximate the area of a circle with the area of an inscribed regular polygon. He calculated the regular 192 polygon.

On the basis of Liu Hui's work, Zu Chongzhi calculated the area of the regular 12288 polygon and the regular 24576 polygon inscribed on the circle, and obtained

3. 14 15926