20以内进位加法是学习多位数计算的基础。要使学生在理解的基础上,熟记20以内进位加法的计算结果,就必须使学生掌握一些计算方法。一、“补数法”。即在第一个加数的基础上补数第二个加数。如9+3,先在脑子里记住9,再伸出3个手指,接着9往下数:10、11、12,故得9+3=12。这种方 Additions within 20 are the basis for learning multi-digit calculations. In order to enable students to comprehend the basis of the merit addition of 20 within the calculation of carry-over, it is necessary to enable students to master some of the calculation methods. First, the “complement method.” That is, the second addend is added on the basis of the first addend. If 9 +3, first remember 9 in the mind, and then extend the 3 fingers, then 9 down the number: 10,11,12, so 9 + 3 = 12. This side