"Willy-nilly" means ignoring everything. Why use this number?

"Willy-nilly" is a common saying, which is popular in many areas such as the Central Plains. Modern Chinese Dictionary explains: "Put all your eggs in one basket and don't ask right and wrong."

Seven, seven, twenty-one, this is a multiplication formula. But why doesn't this proverb say "36 18" or other numbers, but only "372 1"? Jiujiu multiplication table, also known as Xiao Jiujiu, Jiujiu Table, Jiujiu Song, Jiujiu Yin and Jiujiu multiplication table.

At present, primary school students learn from "one by one" to "998 1", but in ancient times it was the other way around, from "998 1" to "one by one". Because the first two words of the formula are "99", people call it "99" for short.

At present, the earliest multiplication formula table found in China is one of more than 30 thousand Qin bamboo slips unearthed in Liye ancient city, western Hunan, which records the multiplication formula in detail. From "998 1" to "two halves combined into one".

China used the "99 formula" earlier. As early as the "Spring and Autumn Period" and "Warring States Period", "99 Ride Songs" had become popular. Sentences such as "3927", "684 18", "483 12" and "6636" can be found in China ancient books such as Xunzi, Guanzi, Huainanzi and Warring States Policy.

During the Spring and Autumn Period and the Warring States Period, not only the Jiujiu watch was invented, but also the decimal system was invented. Later, the East was introduced to Korea and Japan, and then spread to India and Persia in the west through the Silk Road, which became popular all over the world. Decimal system and nine tables are important contributions of ancient China to world culture.

According to the research of mathematical historians, Greece and Babylon, ancient western civilizations, also invented multiplication tables, but they are more complicated than Jiujiu tables. There are more than 1700 Greek multiplication tables invented by Babylon, and they are not complete enough. Because they worked hard to calculate multiplication and division before 13 century, people who can divide large numbers will be considered as experts in mathematics.