Addition and subtraction is selected from the fifth unit of the first volume of senior one mathematics. This unit teaches addition and subtraction within 10. The knowledge of addition and subtraction is often used to solve problems in our daily life. Put it after the addition and subtraction of two numbers within 10. On the one hand, it expands the meaning of addition and subtraction, on the other hand, it also embodies the new curriculum standard that "everyone can get the necessary mathematics"

brief introduction

This is also a difficult content in this unit. Mainly in the calculation process, it is difficult to calculate the results in two steps, especially in the second step, the number calculated in the first step needs to be added and subtracted to complete the calculation task. Moreover, this way of thinking is very helpful to learn the addition of carry within 20.

Example 12 teaches the addition of series according to pumpkin diagram. In teaching, it is suggested that students first talk about what they see on the picture, what kind of mathematical questions they can ask, and how to get the determinant answer after asking. Students will certainly have all kinds of answers. After collecting and summarizing all kinds of answers, the teacher will let the students communicate and tell the meaning of their own formula, and finally sum up the serial addition formula: 4+2+ 1=9.