"Practical problems and linear inequalities of one variable" Inequalities and Inequality Groups PPT Courseware 4

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"Practical problems and linear inequalities of one variable" Inequalities and Inequality Groups PPT Courseware 4

Question 1: In 2002, the ratio of the number of days with good air quality (level 2 or above) in Beijing to the number of days in the whole year was 55%. If the ratio exceeds 70% by 2008, then the number of days with good air quality in 2008 will be at least 10% higher than in 2002. How much increase?

Analysis: Number of days with good air quality in Beijing in 2002__________

Let x represent the increased number of days with good air quality in 2008, then the number of days with good air quality in Beijing in 2008 is ________

Which expression related to x should have a value exceeding 70�?

Tip: There are 366 days in 2008 365×0.55+x/366

Solution: Suppose the number of days with good air quality in 2008 increased by

365×0.55+x/366>70�

Remove the denominator and get x+200.75>256.2

Move items and combine to get x>55.45

Since x should be a positive integer, x≥56

Answer: The number of days with good air quality in 2008 must be at least 56 more days than in 2002, so that the number of days with good air quality in this year can exceed 70% of the total number of days in the whole year.

Question 2: In a knowledge competition, there were 10 quick-answer questions. 10 points were awarded for each correct answer, 5 points were deducted for each incorrect answer, and 0 points were awarded for no answer. Xiaoling did not answer one question, and her score was still no less than 60 points. , at least how many questions did she answer correctly?

Analysis: Score for correct answers - Points deducted for wrong answers ≥ 60 points

Solution: Suppose the number of questions that Xiaoling answered correctly is x, then the number of questions that Xiaoling answered incorrectly is 9-x. According to the meaning of the question, we get

10x-5(9-x) ≥60

Solving this inequality, we get x ≥ 7

Answer: She answered at least 7 questions correctly

Question: How many possibilities does Xiaoling have to answer the question?

Steps to apply linear inequalities of one variable to solve practical problems:

Practical problems----Assume unknowns----Find inequality relations----Line inequalities----Solve inequalities----Determine the answer based on actual conditions

Keywords: Teaching courseware for inequalities and groups of inequalities, teaching courseware for practical problems and linear inequalities of one variable, PPT courseware for the second volume of seventh-grade mathematics published by the New People's Education Press, downloading of seventh-grade mathematics slide courseware, downloading PPT courseware for inequalities and groups of inequalities, practical problems and Download PPT courseware of linear inequalities of one variable in .ppt format

For more information about the PPT courseware "Inequalities and Groups of Inequalities, Practical Problems and Inequality of the First Degree in One Variable", please click on the Inequality and Group of Inequality ppt Practical Problems and Inequality of the First Degree in One Variable ppt tag.

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Update Time: 2024-10-01

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