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《百分数的三种计算问题》是高小算术第四册第二单元《百分数》的教学重点。我过去教学这节教材有以下几点体会: 一、联系旧知识,讲解新知识。百分数的三种计算问题的结构特征和解答方法分别与求一个数的几倍(几分之几)是多少,已知一个数的几倍(几分之几)是多少求这个数,求一个数是另一个数的几倍(几分之几)相同。我在教每一种百分法的计算问题以前,首先复习有关的旧知识,再过渡到新知识的讲解。例如,讲求一个数的百分之几时,先复习了这样两道文字题:15的2倍是多少?15的1/2是多少?明确求15的2倍、求15的1/2都用乘法。然后把1/2改成50％,问15的50％是多少?这样,学生就清楚地认识到求一个数的50％与求一个数的1/2的意义和方法都是相同的。从而初步建立了求一个数的百分之几用乘法的概念。这样联系旧
“Three Percentage Problems” is the teaching emphasis of “Percentage” of the second unit of Book 4 of High and Small Mathematics. I used to teach this section teaching materials have the following experience: First, contact the old knowledge, explain new knowledge. The three types of calculation of the percentage of the structural characteristics and solutions, respectively, and several times a few (a few) is a few, known a few times (a few) is the number of seeking this number, seeking a The same number of times (a few) of another number. Before I teach the calculation of every percentile problem, I first review the relevant old knowledge and then to the new knowledge. For example, how many percent of 15 is 1/2? 15 times the number of 15? multiplication. Then change 1/2 to 50% and ask 50% of 15 how much? So students are clearly aware that finding 50% of a number is the same as having a mean of 1/2. Thus the initial establishment of a few percent of several multiplication concept. This old contact