Improving the speed of mental arithmetic and making it an instinctive natural reaction is the ultimate goal of addition and subtraction mental arithmetic within 100. Proficiency is a process. I learned it in the first semester, and I will continue to learn it in the second year. So I suggest giving up the idea of taking shortcuts. Mathematics is not a subject of memory, and mathematics is not just calculation. The mental arithmetic of addition and subtraction within 100 is based on mental arithmetic of addition and subtraction within 20. Mastering the foundation, mental arithmetic will naturally be fast. Developing thinking is the key content of grade one and two, which is to gradually improve the accuracy, speed and flexibility of oral calculation on the basis of mastering calculation methods.
How to improve the mental arithmetic speed of addition and subtraction within 100?
No matter how big the number is, whether it is mental arithmetic or vertical pen operation, the basis is the addition and subtraction rules and calculation skills within 20, which can greatly enrich students' digital facts and extract them directly in the process of solving problems in the future, saving a lot of cognitive resources. The construction process of digital facts is necessary, provided that the skills are gradually improved on the basis of understanding.
If the main principle of quick calculation and clever calculation in primary school mathematics operation is to round off first and then calculate.
Diversity of calculation methods
In the early stage of understanding, we should advocate the diversification of calculation methods. Only in this way can we gradually optimize on the basis of diversification and form an efficient method that matches ourselves.
Carry addition ~ ten method
Carry addition ~ addition formula
In fact, it is not recommended to recite formulas in the primary stage. Reciting without understanding is not conducive to the real mastery and proficiency of computing skills. You can try to add formulas in the speed-up stage of oral calculation.
Subtraction of abdication ~ ten-break method, ten-flat method
Many methods can be used in the initial stage of abdication subtraction within 20, such as breaking ten, leveling ten, subtraction formula, inverse algorithm, counting and so on, and then through continuous practice, the speed of oral calculation can be gradually improved.