2×3=6

2×4=8

2×5= 10

2×6= 12

2×7= 14

2×8= 16

2×9= 18

3×3=9

3×4= 12

3×5= 15

3×6= 18

3×7=2 1

3×8=24

3×9=27

4×4= 16

4×5=20

4×6=24

4×7=28

4×8=32

4×9=36

5×5=25

5×6=30

5×7=35

5×8=40

5×9=45

2-5 Law of Multiplication and Development of Multiplication Formula;

1, 2-5 multiplication formula law

Numbers 0 and 5 are multiples of 5, numbers 0,246 and 8 are multiples of 2, and the numbers on each number add up to multiples of 3.

Second, the development of multiplication formula

The 99-99 multiplication melody is also often called "Little 99". The formula for students to learn "elementary ninety-nine" is from "11" to "998 1", but in ancient times, it was the other way around, from "998 1" to "11". Because the first two words of the formula are "99", people call it "99" for short. It was only in the 13 and 14 centuries that it became our 99 formula "one get one free" ... 998 1 ".

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

Jiujiubiao, also known as Jiujiuge and Jiuyinge, is the basic calculation rule in multiplication, division, square root and other operations in ancient China. It has been used for more than two thousand years. Pupils and some school-age children can recite it. But Europe didn't know this simple multiplication table until the beginning of 13 century.

In March of 20 15, after the multiplication table of 1999 was introduced into Britain, it was difficult to recite the formula because of different languages. The British version may be changed to "12× 12 multiplication table" after one lesson and one practice.