For example, elementary school math is 35 or 40. Rounding is an accurate counting retention method, which is essentially the same as other methods. But the special point is that rounding can make the difference between the reserved part and the actual value not exceed half of the last order of magnitude. If there is a probability of 0 ~ 9, the total error of this retention method is the smallest for a large number of retained data. This is probably why we regard this method as the basic reservation method.

Interpolation, a method of calculating approximate values, was also first discovered by China. Interpolation is mainly used in functions. It is expressed in modern mathematical language as follows: It is known that the function f(x) has an independent variable X 1, X2,? The corresponding values of Xn are f(X 1) and f(x2)? F(Xn), the method of finding the function value between Xi and Xi+ 1 is called interpolation. If Xn varies equidistantly, it is called independent variable equidistantly interpolation method; If Xn varies by unequal distance, it is called independent variable unequal distance interpolation. This method has a preliminary application in the remaining chapters of Nine Chapters Arithmetic, mainly used to solve linear equations, which is called linear interpolation.