2. Practice step by step, that is, direct addition and subtraction, full five addition, broken five subtraction, carry addition, abdication subtraction, broken five addition and abdication subtraction. The specific formula is as follows:
(1) Formula of addition (how much) Next five addition (how much) into ten addition (how much into one) into five into ten addition (how much into five into one).
(2) Subtraction formula (how many times to how many times) Break five subtraction (how many times to how many times to how many times) Directly retreat ten subtraction (how many times to retreat) Borrow (retreat) ten to make up five subtraction (how many times to retreat).
3, abacus is the foundation, we must practice abacus first. Through the operation of real beads (abacus), we can understand the changes and methods of the four operations. With the proficiency of skills, the image in the brain is gradually established, and the function of mental arithmetic is generated through the analog operation of the image (virtual disk), so the mind is the advanced performance of abacus calculation.
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Abacus mental arithmetic is abacus mental arithmetic. Abacus calculation is a calculation method that uses abacus as a tool to perform operations such as addition, subtraction, multiplication, division and square root. There are certain rules and formulas in the skill of transporting beads. When the user can skillfully operate the abacus, he can not only get the correct answer quickly, but also describe the disk type, grade and floating change of the abacus in his mind through the growth of brain cells. This vivid abacus image is called "virtual disk".
It completes abacus calculation in the brain through the process of perception, image and memory, which is what we call abacus mental calculation. The speed of mental arithmetic is amazing. Often, as long as you hear the number of questions or see the calculation questions yourself, the calculator can blurt out the answers or write them out immediately. Therefore, abacus mental center is an advanced computing technology.
Reference: Baidu Encyclopedia abacus mental arithmetic