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一、教材简析 “多位数加法和减法”这一单元包括多位数加法、多位数减法及加减法速算。 多位数的加减计算方法与万以内加减法的计算方法相同,只是数目较大,数位较多,连续进位和连续退位等情况稍复杂一些。本单元的重点是通过练习,提高学生的计算能力,关键是灵活掌握加减法的运算定律,难点是加减法的速算。
First, textbook analysis “Multi-digit addition and subtraction” This unit includes multi-digit addition, multi-digit subtraction and addition and subtraction speed calculation. Addition and subtraction of multi-digit calculation method is the same as the method of addition and subtraction within million, but a larger number, more digits, continuous carry and continuous abatement and so slightly more complicated. The focus of this module is to improve students' computing abilities by practicing. The key is to flexibly master the law of addition and subtraction algorithms. The difficulty is the speedup of addition and subtraction.