At present, the formula for primary school students to learn "primary ninety-nine" is from "11" to "998 1", while in ancient times it was the other way around, from "998 1" to "224". Because the first two words of the formula are "99", people call it "Xiao 99" for short. It was only in the 13 and 14 centuries that it turned into the present situation.
The characteristics of the extended data table 99
General 1 and 99 tables only use 9 numbers from 1 to 9.
2. Jiujiu table contains the commutativity of multiplication, so only 8972 is needed, and "9872" is not needed. 9 times 9 has 8 1 product, and the 99 table only needs 1+2+3+4+5+6+7+8+9 =45 product. In the Ming Dynasty, abacus also had 99 tables with 8 1 product. The 99 table of 45 items is called small 99, and the 99 table of 8 1 item is called big 99.
3. The shortest multiplication table in the ancient world. Maya multiplication table must have 190, Babylon multiplication table must have 1770, and Egypt, Greece, Rome, India and other countries must have infinite multiplication tables; Only 45/8 1 item is needed for the 99 table.
Baidu encyclopedia-multiplication formula table