“100以内的加减法”这一单元的教学重点是两位数加、减一位数的口算,以及两位数加、减两位数的笔算。这些内容是学生今后进一步学习整数四则运算的基础,是必须练好的基本功。两位数加、减一位数或整十数的口算这部分教学内容,教材是各分三段来编排的。第一段,学习两位数加、减一位数的不进位加法和不退位减法。如:21+6=27,28-5=2。第二段,学习两位数加、减整十 “Less than 100 addition and subtraction” This unit focuses on the teaching of double-digit plus and minus one-digit port count, as well as double-digit plus and minus two-digit calculations. These contents are the basis for students to further learn the arithmetic of integer numbers in the future and are the basic skills that must be practiced. Two-digit plus, minus one digit or the whole number of mouth this part of the teaching content, textbooks are arranged in three sections. The first paragraph, learning two-digit plus, minus one-digit non-carry addition and non-withdrawal subtraction. Such as: 21 +6 = 27,28-5 = 2. The second paragraph, learning two-digit plus, minus ten