从历史的角度看,长度单位的建立是一个由随性走向规范、由个性走向统一的过程。教学长度单位的认识,其核心环节有三个:一是体会建立统一度量标准的重要性,二是建立关于该标准实际长度的清晰表象,三是用学习的长度单位进行简单的测量。事实上,苏教版教材所安排的教学活动也正是围绕这几个关键环节来展开的。那么,怎样才能将长度单位由随性 From a historical point of view, the establishment of length units is a process of going from nosy to norm and from personality to unity. Teaching length unit of understanding, its core links there are three: one is to understand the importance of establishing a unified measurement standards, the second is to establish a clear representation of the actual length of the standard, the third is to use the length of the learning unit for simple measurements. In fact, the educational activities arranged by the teaching materials of the Supian textbooks are also carried out around these key links. So, how can the length of units from casual