"Average and Weighted Average" PPT courseware

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"Average and Weighted Average" PPT courseware

1. Generally, we call the ratio of the sum of n numbers x1, x2,...,xn to n the arithmetic mean of these n numbers. The abbreviated mean is recorded as

2. The importance of each data in a set of data is not necessarily the same. When calculating their average, each data is often given a "weight", and the average calculated from this is called a weighted average.

3. If the weights of n data x1, x2,...xn are w1, w2,...wn respectively, then the weighted average of these n numbers is x1w1+x2w2+....+xnwn/w1+w2+...+wn

1. (5 points) The daily maximum temperatures (unit: ℃) of a certain city in a certain week are: 25, 28, 30, 29, 31, 32, 28. The average daily maximum temperature of this week is ()

A． 28℃B. 29℃　C． 30℃　D. 31℃

2. (5 points) (2013·Dalian) In a "Love and Mutual Aid" donation activity, the amount of donations (unit: yuan) donated by 8 students in the first group of a certain class is as shown in the following table:

The average amount of donations from these 8 students is ()

A． 3.5 yuan B. 6 yuan C． 6.5 yuan D． 7 yuan

3. (5 points) In recent years, the number of civilian cars in Yiwu has continued to grow. From 2009 to 2013, the number of civilian cars in Yiwu was approximately: 15, 19, 22, 26, x (unit: 10,000 vehicles). These five The average of the numbers is 22, then the value of x is _______.

4. (5 points) (2013·Zhuzhou) A certain recruitment examination is divided into two types: written test and interview. The written test is 60% and the interview is 40%. The weighted average is calculated as the total score. Kong Ming’s written test score is 90 points and the interview score is 85 points. Then Kong Ming’s total score is ___ points.

【Error-prone Inventory】

[Example] The mathematics scores of the ninth grade midterm exam are as follows: Class 9 (1) has 55 students, with an average score of 81 points; Class 9 (2) has 40 students, with an average score of 90 points; Class 9 (3) has 45 students, with an average score of 85 points; There are 60 students in Class 9 (4), with an average score of 84. Find the grade average.

[Incorrect explanation] Suppose the average grade score is x, then x = × (81 + 90 + 85 + 84) = 85 (points)

[Error Cause Analysis] The error is that the number of people in each class is different, that is, the "importance" of each number is different, so the weighted average of this set of data should be calculated.

【correct】

(1) After the game, A guesses that the scores for the four items of tangram puzzle, clever solutions to interesting problems, mathematical applications, and Rubik's Cube recovery will be converted into the total score at 10%, 40%, 20%, and 30% respectively. Based on the guess, find A’s total score;

(1) According to the meaning of the question, the total score of A is:

66×10%+89×40%+86×20%+68×30%=79.8 (points)

(2) The organizing committee of this competition decided that students with a total score of 80 points or more (including 80 points) will win the first prize. It is now learned that the total scores of B and C are 70 points and 80 points respectively. The sum of the converted scores for A's tangram puzzle and Rubik's Cube recovery is 20 points. Can A win the first prize in this competition?

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"Average and Weighted Average" PPT courseware 3:

"Average and Weighted Average" PPT courseware 3 (1) Observation and thinking Divide an experimental field into 8 equal areas, each 100m2, and try to plant two different varieties of wheat under the same conditions of soil fertility, fertilizer, management, etc. , the output is as follows: 1. From Figure 261..

"Average and Weighted Average" PPT Courseware 2:

"Average and Weighted Average" PPT Courseware 2 When calculating the weighted average based on the frequency distribution table, the ________ of each group is commonly used in statistics to represent the actual value of each group, and the ______ of each group is regarded as the value in the corresponding group The right of value. 1. (4 points) Among the following sets of data, in the group...

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Update Time: 2024-10-19

This template belongs to Mathematics courseware Hebei Education Edition Ninth Grade Mathematics Volume 1 industry PPT template

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