Find out the number of left behind children in a village and the education of their parents

Solution: (1) The number of classes in the school is 4 20% = 20 (pieces), and the number of classes with only 2 left-behind children is: 20-(2+3+4+5+4)=2 (pieces), and the average number of left-behind children in each class of the school is:

1 2 + 2 2 + 3 3 + 4 4 + 5 5 + 6 420 = 4 (name), the supplementary figure is as follows:

2) From (1), there are 2 classes with only 2 left-behind children, with a total of 4 students A1, A2 from one class, B1, B2 from one class, from the dendrogram, it can be seen that there are 12 possible situations, and the probability of each outcome is equal, among which there are 4 cases from one class, then the probability of the two left-behind children selected from the same class is: 412=13

I think it is mainly analyzed from the aspects of urban development, family economy, traditional parents' pension, work pressure, and insufficient educational resources. The specific reasons are as follows:

1.Urbanization: As urbanization accelerates, many families have left their homes in search of better working and living conditions, leaving many children behind in rural areas.

2.Families are in financial difficulty: Many families are financially poor and cannot afford to pay for their children's education in the city, so they have to leave their children at home in rural areas.

3.Parental retirement: As the Chinese population ages, more and more young people have to return to their hometowns to care for their elderly parents, and these children remain in the countryside as a result.

4.Stress of work: Many parents need to go out to work in order to make a living, and they can only leave their children at home after being away from home for a long time.

5.Inadequate educational resources: Rural areas have relatively few educational resources, and many parents find it more convenient and affordable to stay at home for education.

Solution: (1) 4 20% = 20 (pcs); 20-2-3-4-5-4=2,(l 2+2 2+3 3+4 4+5 5+6 4) 20=4

A: The school has an average of 4 left-behind children per class.

2) Because there are only 2 left-behind children in the class, there are only two classes: Class A and Class B. The 2 left-behind children in the Speeder class are A1

The two left-behind children in Class A2B are BL

The B2 list is as follows:

From **, it can be seen that there are 12 situations. Eligible are a1a2a1a2b1b2b2b1

b2 four, 4 12 = <>

A: The probability of selecting two left-behind children from the same class is <>

(1) 4 people; （2） 1/3。

Test question analysis: Solution: (1) The number of classes in the school is: 4 20 = 20 (pieces) The number of classes with only 2 left-behind children is: 20-(2+3+4+5+4)=2 (pieces) The average number of left-behind children in each class of the school is:

<> from drawing the tree diagram, it can be seen that there are 12 possible situations, of which 4 are from the same class, so the probability of the two left-behind children selected from the same class is p=<>

Comments: This question is relatively simple, and you should develop a certain ability to read pictures in your usual practice.

Solution: (1) The number of classes in the school is: <>

The number of classes with only 2 left-behind children is: 20-(2+3+4+5+4)=2

The average number of left-behind children in the school is <>

The supplementary figure is as follows:

2) From (1) it is known that there are only 2 left-behind children in the class, there are 2 classes, a total of 4 students.

The <> comes from a class, <>

From another class, the list is as follows:

According to the list, there are 12 possible situations, and 4 of them are from the same class.

Therefore, the probability that the two left-behind children selected will come from the same class is <>

1) The number of classes in the school is 4 20%=20 (pieces), and the number of classes with only 2 left-behind children is: 20-(2+3+4+5+4)=2 (pieces), and the average number of left-behind children in each class of the school is:

4 (name), the supplementary figure is as follows:

2) There are 2 classes with only 2 left-behind children from (1), a total of 4 students A1 A2 from one class, B1

B2 comes from a class, <>

According to the dendrogram, there are 12 possible scenarios, and the probability of each outcome is equal, and if there are 4 scenarios from one class, the probability of the two left-behind children selected from the same class is: 4