“异分母分数加、减法”是在学生熟练地掌握了通分和同分母分数加、减法的基础上进行教学的。同分母分数加减法和异分母分数加减法的计算方法虽然有所不同,但计算思路却是一致的,即必须是相同的计算单位才能相加、减。而这正是新旧知识的联结点。因此抓住知识的内在联系,以转化为主线,一步步引导学生掌握异分母分数加减法的法则,进一步提高计算能力,将成为本节教学的基本思路。 1、复习铺垫,引入新课 复习通分和同分母分数加减法等知识,为知识的延伸做好准备。 2、巧妙设疑,引入课题。将同分母分数的加法算式改写成异分母分数的加法算式,让学生计算,激发学生的求知欲,唤起他们的学习兴趣。 二、迁移类推,学习新知 1、讲解例1 (1)出示例1,启发提问:①1/2和1/3的分数单位相同吗?②不同分 “Different denominator score plus, subtraction” is based on the students master the pass points and the same denominator score plus, subtraction based on the teaching. Although the calculation method of addition and subtraction with the denominator and the addition and subtraction with different denominators are different, the calculation ideas are the same, that is, the calculation units must be the same and can be added and subtracted. And this is the juncture between old and new knowledge. Therefore, grasping the intrinsic link of knowledge and transforming it into the main line, we should guide students to master the law of addition and subtraction of different denominators step by step so as to further improve their computing abilities. This will become the basic idea for teaching in this section. 1, review the bedding, the introduction of the new lesson pass points and the same denominator fractional addition and subtraction and other knowledge, to prepare for the extension of knowledge. 2, ingenious doubts, the introduction of topics. The addition of denominator fractions is rewritten as an addition formula with different denominator scores to enable students to calculate, stimulate their curiosity and arouse their interest in learning. Second, the transfer of analogy, learning new knowledge 1, explain Example 1 (1) Example 1, inspired questions: ① 1/2 and 1/3 of the same score units? ② different points