The quantitative relationship is a mandatory part of the public service examination, and it is also a more difficult section, and most candidates basically choose to give up the quantitative relationship in the examination process, first because the questions are more difficult, and secondly, the time is tighter. However, under such great competitive pressure, if you want to stand out from the crowd, then the number is the part that pulls the score. In the quantitative relationship, a class of problems will be examined almost every year, that is, the permutation and combination problem, if you want to solve the permutation and combination problem, you must master a certain method, and today we will share with you a method is the first method.
1. What is permutation and combination?
Permutation and combination problems are actually a kind of questions that the questioner loves in the public service examination, his essence is actually a counting problem, usually in the question, we will be asked how many kinds of situations, methods, and results, at the beginning we solve this kind of problem through the form of enumeration, but because sometimes there are too many situations, it is not easy to enumerate, so this kind of counting problem is solved by permutation and combination. Permutation means that we select m elements from n different elements, and see how many cases there are, and the permutation is expressed as
with
2. How to solve permutations and combinations
In the process of the exam, the permutation and combination questions are relatively tricky, and the questioner will always have a variety of requirements when he asks the question, such as sometimes there will be a requirement that some elements must be adjacent, at this time, we can take a way to solve this kind of problem, that is, the ** method, and then we will consolidate it through some example questions.
Example 1] 6 people are lined up in a row, where A, B and C must be next to each other, how many ways are there to stand?
a.120 b.144 c.156 d.169
Answer] B. Analysis: From the meaning of the topic, it is required that A, B and C must be adjacent, and the ** method can be adopted, A, B and C travel as a whole, and the other three people have 4 parts of the trip, there are sequential requirements, so there are
24 kinds, next consider the internal A, B, C three, there are also order requirements
6 kinds, step-by-step process, so there are 24 6 = 144 kinds, choose option b.
Example 2] A science and technology forum has 5 themes: 5G, artificial intelligence, blockchain, big data and cloud computing, and each topic has 2 speakers. If the order in which panelists for each topic are required to speak next to each other, how many different speaking orders are there?
a.120 b.240 c.1200 d.3840
Answer] d. Analysis: From the meaning of the topic, it is required that the order of the speakers of each theme must be adjacent, and the ** method can be adopted, and five different themes ** form 5 wholes, and there are order requirements, then there are
120 kinds, let's consider the interior, there are 2 guests for each topic, inherent 2 2 2 2 2 = 32 kinds, step-by-step process, so there are 120 32 = 3840 kinds, choose option d.
Today I have introduced to you the method of solving the problem of permutation and combination, and pay attention to whether there are order requirements between the overall internal elements in the application process. I have mastered the ** method, and I hope to help us get the score when we encounter permutations and combinations in the exam room!
If you have mastered more ways to solve the problem, then I believe you will be able to stand out among the candidates and go ashore smoothly!