10.2 count and probability basis

1. Principle of addition:

There are n methods to do one thing. Step I has a PI solution, and there is a total of P1 + p2 + ...... + PN Solutions

2. multiplication principle:

To do one thing, you need to divide it into n steps. In the first step, there are M1 different methods, and in the second step, there are M2 different methods ,......, There are different Mn methods for Step n. So there are n = m1 × m2 × m3 ×... * Mn methods. The addition principle is the basic principle of mathematical probability.

3. Refresh principle:

When counting, you must note that there is no repetition and no omission. In order to prevent overlapping parts from being repeatedly calculated, people have developed a new counting method. The basic idea of this method is to ignore the overlap first, calculate the number of all objects contained in a certain content first, and then exclude the number of repeated computations during counting, so that the calculation results are no omissions or duplicates, this counting method is called the refresh principle.

A branch B Branch C = A + B + C-a branch B-B Branch C-c branch a + A branch B Branch C

4. Full arrangement of repeated elements:

[Description] There are k elements, and the I-th element has Ni. The number of fully arranged elements is required.

[Analysis]

5. Reusable combinations:

[Description]

[Analysis]