Gǔ / rén / cháng / yòng / zhōu / sān / jìng / yī / lái / jìn / sì / shuō / míng / yuán / de / zhōu / cháng / hé / zhí / jìng / guān / xì

古人常用“周三径一”来近似说明圆的周长和直径关系。

Ancient people often used “周三径一” as an approximation of the relationship between a circle's circumference and diameter.