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“甲组3人割草24千克,乙组2人割草6千克,平均每人割草多少千克?”当学生列出下列算式时, 算式一:(24÷3+6÷2)÷2=5.5(千克) 算式二:(24+6)÷(3+2)=6(千克) 教师如何进行讲评呢? 如果只是从求平均数的数量关系“总数量÷总份数=平均数”说明算式一错误,学生肯定一知半解,甚至迷惑不解。因为在他们脑海中,求平均数的数量关系就是等分关系。从感知基础上理解求平均数的意义就是移多补少。现在从二组中各取1人的平均割草量进行移多补少的等分,为什么错呢?如果不错,那么计算结果为什么与算式二不同呢?所以这个困惑单凭数量关系进行讲评说服力不够。我在教学时借助图
“A group of three people mowing 24 kilograms, 2 people in Group B mowing 6 kilograms, the average number of mowing each kilogram?” When students listed the following formula, the formula one: (24 ÷ 3 + 6 ÷ 2) ÷ 2 = 5.5 (kg) Formula 2: (24 + 6) ÷ (3 + 2) = 6 (kg) How can teachers comment? If only from the relationship between the number of averages “total quantity ÷ total number of copies = average” Explain the formula an error, the students must know little or nothing, even puzzled. Because in their minds, the quantitative relationship between the average is the relationship between the equinoxes. Understand the meaning of the average from the perspective of perception is to move more to add less. Now from the average of two people in each group of 1 mowing the amount of more compensation for the addition of less, why wrong? If so, why the calculation results are different from the formula two? So the confusion alone to discuss the relationship between quantitative persuasion Not enough power. I use the diagram when teaching