一、问题《义务教育数学课程标准(2011年版)》将第一学段的估算教学目标修改为“能结合具体情境,选择适当的单位进行简单估算,体会估算在生活中的作用”。人教版教材据此做了相应的调整,在三年级上册“万以内数的加法和减法(一)”这个单元增加了用估算解决问题的教学内容例4(如图1)。这个增加的教学内容,让教师们在教学实践中产生了众多的困惑与问题。 First, the question “compulsory education mathematics curriculum standards (2011 Edition)” the first paragraph of the assessment of teaching objectives revised to “can be combined with specific situations, select the appropriate units for a simple estimate, experience estimating the role in life ”. According to this, the PEP teaching material has been adjusted accordingly. In the third grade, the unit of “Addition and Subtraction of Within One Hundred and Thousands” added an example of teaching content 4 (Figure 1). This increase in teaching content, so that teachers in teaching practice has had many problems and confusion.