Mathematics for the second year of junior high school The following table is the statistical table o

2. Find out the average score of the students who got the scores.

82+ points) This step is wrong.

The correct one is [82*20-(60*1+70*5+100*2)] 12=There is no need for this step, skip directly to the third step, and your third step is also wrong.

3. Find out the total score of the students who got the scores.

The total score should be: 82*20-(60*1+70*5+100*2)=1030

4. Make a list of equations.

x+y=12

80x+90x=1030

The solution is x=5 y=7

To sum up: your thinking is wrong, and in the end, you should go back to the standard answer.

The first step starts to get wrong. Don't think like that. This question must start with the average grade and the number of people known.

In the question, it is said that the average score of 20 people is 82, then you first directly seek their total score, 20 * 82 = 1640 points, that is, 60 * 1 + 70 * 5 + 80 x + 90y + 100 * 2 = 1640

Then, because the number of people who know that they have a score is 1+5+2=8, there is x+y=20-8

The solution can be found by solving the binary equation according to these two equations.

You are wrong in step 2, find the average score of 80 90, and use (total score known score) (number of people from 80-90) i.e.

82*20 (60*1+70*5+100*2)] 12=So you're wrong.

The average grade of the student seeking the score should be:

Then the total score of the students who scored is as follows:

Step 2 started wrong. The first step is the average score of 8 people, but the second step is the average score of 12 people, not just +. If there are 10 people at the same time, the average score is OK. I should forget about my own meeting later.

The above formula is simplified to:

x+y=12...1)

8x+9y=99...2)

2) 8-(1) Dept.

y=3 is brought in (1). x=9

Finishing gets.

x+y=12 （1）

8x+9y=99 (2)

2)-(1)*8.

y=3 and then bring in (1) to get. x=9

Equation 1: 8+x+y=20 to get x+y=12 i.e. x=12-y Equation 2: 60+350+80x+90y+200=1600 8x+9y=99 8(12-y)+9y=99 96-8y+9y=99

y=3,x=9

It's the first time I've played so much, so tired.

(1) From the median, it can be seen that 85 points rank after the 25th place, and it cannot be said that 85 points are upstream in terms of rank; But you can't judge the quality of learning simply by rank, Xiao Gang scored 85 points, indicating that he has a good grasp of the learning content of this section, and it can also be said to belong to the upstream in terms of mastering the learning content;

2) The median score of the third (1) class of junior high school is 87, indicating that more than half of the students have a score higher than 87, and the average score is 79 points, and the standard deviation is very large, indicating that there are many low scores and serious polarization, and it is recommended to strengthen the help for those with learning difficulties;

The median and average scores of the third (2) class were both 79 points, and the standard deviation was very small, indicating that there were few students with poor learning, but there were also few students with excellent learning, and it was recommended that measures be taken to improve the excellent rate

(1) According to the title:

1+5+x+y+2=20

x+y=12

8x+9y=103

The solution is x=5

y=7A: x=5, y=7;

2) From (1) know that a = 90 points, b = 80 points

A: The mode is 90 points and the median is 80 points

Solution: (1) According to the topic: <>

The solution is <>

Answer: x=5, y=7;

2) From (1) know that a = 90 points, b = 80 points

A: The mode is 90 points and the median is 80 points

Solution: (1) According to the problem: 1+5+x+y+2=2060 1+70 5+80x+90y+100 2=82 20

Answer: x=5, y=7;

2) From (Nazhi 1) know a = 90 points, b = 80 points Answer: The mode is 90 points, and the median is 80 points I hope it will help you.

(1) Simultaneous equations.

60+70*5+80x+90y+100*2=82*20{ x+y=20-(1+5+2)

The solution is x=5 y=7

2) Because there are 7 people with a score of 90, the most, so the mode a=9020 people score from small to large, the 9th, 10th is 80, so the median b=80

60*1+70*4+80x+90y+100*3)/20=851+4+x+y+3=20

The solution yields x= 2 y= 10

2) Because there are 10 people with a score of 90, the most, so the mode a=9020 people score from small to large, the 9th and 10th places are 90, so the median b = 90 (60-85) square + (70-85) square * 4 + (80-85) square * 2 + (90-85) square * 10 + (100-85) square * 3] 20 = 125, so the value of s square is 125