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苏教版《数学》四年级上册“除法”第一课时的教学内容是“除数是整十数的口算”。根据例题的主题图(如下图),学生很容易列出算式“60÷20=”。结果是多少呢?学生的回答通常有这样几种:把60和20末尾的0去掉,先算6÷2,再在结果后面加一个0;3×20=60,所以60÷20=3;60÷10=6,6÷2=3;60-20=40,40-20=20,20-20=0,所以60÷20=3;……这道例题教学的着力点在哪里?当然是理解口算的算理。这些方法中,最核心的算
The Soviet version of “Mathematics” fourth grade on the book “division ” The first class teaching content is “Divisor is the whole number of mouth count ”. According to the subject of the theme map (below), students can easily formulate “60 ÷ 20 = ”. What is the result? The students usually have the following answers: Take 0 at the end of 60 and 20, calculate 6 ÷ 2, add 0 after the result; 3 × 20 = 60, so 60 ÷ 20 = 3; 60 ÷ 10 = 6,6 ÷ 2 = 3; 60-20 = 40, 40-20 = 20, 20-20 = 0, so 60 ÷ 20 = 3; ...... The focus of this example teaching where? Is to understand the calculation of mouth arithmetic. These methods, the core of the count