English: trachtenberg law

Attribute: Mathematics

Founder: Yakov trachtenberg

Time of appearance: during World War II

Basic interpretation: ① belongs to a fast mental arithmetic system, ② consists of several easy-to-remember operations, and the general multiplication, division, addition and subtraction are also involved. Compared with ordinary calculation methods, it has higher spatial uniformity.

Detailed explanation: With the number 57× 135, you should work out the answer of 7695. First of all, the last few numbers, that is, 135×57. Multiply the two single digits 7 and 5 to get 35, take the single digit 5 of the answer as a reservation, multiply the previous digits from right to left, take the single digit and then take the ten digits. Take the unit number of 7×3 1 and the decimal number of 7×5 in the previous step and add it to the unit number of 5×5 to get the answer 9. (Note here that the remaining ten digits of the second-step answer should be added to the third-step answer. ) And so on, it is 7× 1. Take the decimal digits 2 of unit digits 7,7× 3, 5×3 and 5×5, and add them to the decimal digits 0 of the previous answer to get the answer 16. Only the numbers 5, 3 and 1 remain. Take out the unit number 5 of 5× 1 and the decimal number 1 of 5×3, and add the reserved number 1 to get the answer 7. The final result 7695 can be obtained after this sorting. The advantage of this arithmetic method is that you only need to know the multiplication table and simple counting.

Quick mental arithmetic-referred to as quick mental arithmetic, also called "oral arithmetic". One of mathematics teaching methods. A calculation method based on thinking and language activities without any tools. It can cultivate students' quick calculation ability and develop their attention, memory and thinking ability. Proficiency in verbal calculation is helpful for written calculation and is convenient for daily use. Fast center is the only way to perform simple operations without any physical objects, abacus, fingers, chessboard and charts.

Fast mental arithmetic is different from abacus mental arithmetic and palm mental arithmetic. Mainly through certain rules in textbooks, children are trained to operate quickly in addition, subtraction, multiplication and division. "Quick mental arithmetic" is helpful to improve the order, logic and sensitivity of children's thinking and behavior, and train children's eyes, hands and brain to react synchronously and quickly. The calculation method is consistent with mathematics in primary and secondary schools, so it is very popular with parents of young children.

References:

Quick mental arithmetic-Baidu encyclopedia