【教学案例】师出示第一道题:一根绳长3米,分成5段,每段绳长占全长的几分之几?全体学生在自己的练习本上很快写出答案。师:有不同意见吗?生:没有。师:我们班解答这道题的结果是全军覆没。(全班哗然,几位机灵的学生好像意识到问题的所在)生:这道题没有说明是否把绳子进行了平均分,所以每段的绳长占这根绳子的几分之几是不确定的,是无法 【Teaching Case】 The teacher shows the first question: A rope is 3 meters long, divided into 5 sections, each section of rope length accounting for a few of the total length? All students in their own exercise book quickly write the answer. Teacher: Do you have any different opinions? Teacher: The result of our answer to this question in our class is annihilation. (The class uproar, several clever students seem to be aware of the problem) Students: This question does not say whether the rope was averaged, so the rope length of each paragraph accounted for a few of the rope is uncertain It is impossible