C (5,3)
=(5*4*3)/(3*2* 1)
= 10
This is a question of permutation and combination, which 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.
Extended data:
Basic counting principle:
Addition principle sum classification counting method
1. addition principle: There are n ways to do one thing, and finish it. In the first way, there are m 1 different ways, in the second way, there are m2 different ways, ... and in the n ways, there are mn different ways, so there are N = m 1+M2+M3+ to complete it.
3. The method of the first method belongs to the set A 1, the method of the second method belongs to the set A2, ... and the method of the n method belongs to the set An, so the method of completing it belongs to the set A 1ua2u...uan.
3. Classification requirements: each method in each category can accomplish this task independently; The specific methods in the two different methods are different from each other (that is, the classification is not heavy); Any method to accomplish this task belongs to a certain category (that is, classification does not leak).
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