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一、缘起最近,在我校组织的“同课异构”活动中,笔者和另一位年轻教师“同台竞技”。我们上课的内容是《乘法和加、减法的两步混合运算》(苏教版四年级上册)。教材先让学生解决购物情境中的两个实际问题(列式为:3×5+20和50-2×18),试图结合数量关系的分析体会“乘法和加、减法的两步混合运算”的运算顺序及其合理性。在此基础上,概括出运算顺序:算式中有乘法和加、减法,应先算乘法。
First, the origin Recently, organized by our school “Lesson heterogeneous ” activities, the author and another young teacher “on the same stage ”. The content of our class is “two-step mixed operation of multiplication and addition and subtraction” (Sujiao Grade Four). The textbook first allows students to solve two practical problems in the shopping context (columns: 3 × 5 + 20 and 50-2 × 18), trying to combine the quantitative relationship analysis to understand the “multiplication and addition, subtraction, two-step hybrid computing ”The order of operation and its rationality. On this basis, summarizes the order of operations: arithmetic multiplication and addition, subtraction, should be the first calculation multiplication.