【利弊分析】北师大版小学数学第四版教材二年级下册第五单元是学习三位数的加减法,为了有效的提高学生关于两三位数的计算技能,尤其是口算技能,教材第一次介绍利用数线这个直观模型进行口算。借助数线口算是一种新的方法,它有以下几个优点:第一、借助数线可以将口算顺序直观化,条理清晰,有利于增强学生对口算算理的理解,非常适合多位数的加减法口算。如计算321+258,就这样画数线: Advantages and Disadvantages Analysis】 【Beijing Normal University version of the fourth edition of the fourth edition of textbooks Volume two of the fifth unit is to learn the addition and subtraction of three digits, in order to effectively improve the students on the calculation of two or three digit skills, especially oral calculation skills, Teaching materials for the first time introduce the use of a few lines of this intuitive model mouth count. With the number of lines and mouth is a new method, which has the following advantages: First, with the help of several lines can be straightforward sequence of the mouth count, clear, help to enhance students’ understanding of the mathematical calculation, is ideal for multi-digit Addition and subtraction method of calculation. Such as calculating 321 +258, so draw a few lines: