万以内的连续退位的笔算减法是《万以内的加法和减法（二）》这一单元的一个重点，也是教学的一个难点。“中间、末尾有零的退位减”由于各个数位上的数的变化情况比较复杂，算理的理解难度较大，学生计算时容易出错，因此，在教学时，教师应遵循学生的认知规律，铺路架桥... The arithmetic subtraction method of successive abortions within a million is a key point in the unit of “addition and subtraction within ten thousand (two)” and is also a difficult point in teaching. “The middle, the end of a zero abatement minus” Because of the changes in the number of each digit is more complex, difficult to understand the comprehension of mathematics, students prone to error when calculating, therefore, teachers should follow the cognitive rules of students , Paving bridge