“20以内进位加法与退位减法”的教学问题,本人一直在进行摸索。我也曾把“口诀法”与“凑十法”进行了对比。通过对比,从中看出“口决法”优于“凑十法”,但也存在一些问题,需要进一步改进。(一)使用“口诀法”的必要性“20以内的进位加法”一般采用凑十法、减补法、记大数小法等三种教法。现行教材则采用凑十 “20 addition and subtraction within the carry-in subtraction” teaching, I have been exploring. I have also compared the “formulas of the tactics” with “the ten methods”. By comparison, we can see that the “verdict” is superior to the “ten-sum method”, but there are also some problems that need further improvement. (A) the use of “the tactics” necessity “Carry within less than 20 plus” generally use Minato law, subtraction of law, remember the small number of law and other three kinds of teaching. The current textbook is Minato ten