"Brocade" is the calculation method of the product of two numbers. It is said that this method first appeared in a book by Pushkar, an ancient Indian mathematician. After AD 12, it was widely spread in areas where Arabs lived in compact communities, and then spread to Europe through Arabs, and soon became popular in Europe.

/kloc-In the middle of the 5th century, the Italian mathematician pacioli introduced this method in his book "Summary of Arithmetic, Geometry and Proportional Properties", which was then called "lattice multiplication". China, a descendant, was also very popular in the future and was favored by the North Korean mathematician Cheng Dawei, who absorbed him into the famous book Arithmetic Unity.

Calculation method:

Draw a rectangle first, divide it into m×n squares (m and n are the digits of two multipliers respectively), and write down two factors on the top and right side of the square respectively. Then divide the square into two parts by diagonal, and record the ten digits and single digits of the product corresponding to the above numbers respectively. Then these products are added diagonally from the bottom right to the top left, and when they reach ten, they move forward by one. Finally, the result is obtained (the numbers on the left and bottom of the box are arranged in turn).

In Arithmetic Unity, we talked about "writing and calculating", that is, "paving the way". This is a way to write on a pre-drawn grid. This method was popular in India, Arabia and Europe, and was introduced to China in about15th century. As a result of writing and calculation, numbers are arranged densely and orderly like brocade, so people call it "brocade".