1, practice the operation in 10, which is the basis of carry abdication operation. The operation within 10 is easy to make clear, otherwise the operation after 10 will be very chaotic.

2. Let children know the structure of two digits, and distinguish between "ten digits" and "unit digits", such as "14", including a "10" and a "4", especially the "1" of ten digits, and understand that it stands for "/kloc-0". ?

3. The operation of two digits is suitable for the combination of "horizontal" and "vertical". The relationship between vertical ten digits and unit digits is more obvious. Instead of telling these "terms" to children, let them understand them through sensibility.

Fast calculation skills of two-digit addition and subtraction;

Two-digit addition formula: add 9 minus 1, add 8 minus 2, add 7 minus 3, add 6 minus 4, add 5 minus 5, add 4 minus 6, add 3 minus 7, add 2 minus 8 plus/kloc-0 minus 9.

Subtotal formula for abdication of two digits: minus 9 plus 1, minus 8 plus 2, minus 7 plus 3, minus 6 plus 4, minus 5 plus 5, minus 4 plus 6, minus 3 plus 7, minus 2 plus 8 minus 1 plus 9.

Fast calculation refers to a fast calculation method that uses the special relationship between numbers to perform fast addition, subtraction, multiplication and division operations, and uses a thought and a method to perform addition, subtraction, multiplication and division operations on any number quickly and accurately. This operation method is called speed algorithm and heartbeat algorithm.