The analysis process is as follows:

Suppose three people are ABC. There are six sitting methods: ABC, ACB, BAC, BCA, CAB and CBA.

Or suppose A takes a seat first, and there are three positions to choose from.

Then b found a seat and sat down. Besides the position of A, there are two options. ..

Finally, C takes a seat, except for the positions of A and B, there is only one position.

Therefore, the total * * * is 3×2× 1=6 species.

Extended data:

To do one thing, it needs to be divided into n steps. There are m 1 different methods to do the first step, m2 different methods to do the second step, ... and mn different methods to complete the n step. So * * * is N=m 1×m2×m3×…×mn to accomplish this? Different methods. And addition principle are the basic principles of mathematical probability.

The calculation method of permutation and combination is as follows:

The arrangement a (n, m) = n× (n- 1). (n-m+ 1) = n！ /(n-m)！ (n is subscript and m is superscript, the same below)

Combination C(n, m)=P(n, m)/P(m, m) =n! /m！ (n-m)！ ;

take for example

A(4，2)=4！ /2! =4*3= 12

C(4，2)=4！ /(2! *2! )=4*3/(2* 1)=6