First, write. Arranging and combining requires strong logical thinking, and every situation needs to be considered. Because people's imagination has certain limitations, some situations may be left behind or cannot be counted. At this time, we will start writing, not only drawing, but also calculating and counting. Some simple statistics may make it very troublesome to calculate numbers. At this time, it is very important to list all possible situations and then calculate the total.

Secondly, there are ways to arrange and combine, such as "inserting spaces", which are used when the condition of "not adjacent" is required in the title, but it can also be every few non-adjacent, and another example is "binding method" (different places seem to be called differently). If two or more must be adjacent to each other, first tie them together as a row. After this row is over, tie the tied ones together. The method mainly depends on what the teacher teaches and summarizes himself, and what kind of questions and methods will get twice the result with half the effort.

Thirdly, clear your mind, whether it is permutation and combination or other math problems, you should clear your mind, and you can't just write down a condition or a situation, if it is useful. Every problem has the most direct way of thinking. For example, to find the volume of a cylinder, first find the radius, then the bottom area, and then the volume, and the arrangement and combination are the same. According to the characteristics of the problem, we should have our own way of thinking, whether to find the red ball or the white ball first. The thinking must be clear and must not be confused. If we are confused, it is easy for us to repeat or miss this situation.

Permutation and combination is the most basic concept of combinatorics. The so-called arrangement refers to taking out a specified number of elements from a given number of elements for sorting. Combination refers to taking out only a specified number of elements from a given number of elements, regardless of sorting.

The central problem of permutation and combination is to study the total number of possible situations in a given permutation and combination. Permutation and combination are closely related to classical probability theory.

Although mathematics began in ancient times, there was no skill because the development of social production level was still in the low stage. With people's understanding and research on numbers, in the process of forming mathematical branches closely related to numbers, such as the formation and development of number theory, algebra, function theory and even functional, the diversity of numbers is gradually discovered from the diversity of numbers, and various counting skills are produced.