Simple method of 798+43 1-598+369

The simple method of 798+43 1-598+369 can use the speed algorithm.

Four numbers are known: 798,431,598,369. First, we can add two positive numbers and subtract the result of adding two negative numbers: 798+43 1-(598+369)=262. Then, we found that we can add 798 and 598 first, and then subtract 4398.

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Mathematical speed algorithm refers to the calculation method of fast addition, subtraction, multiplication and division by using the special relationship between numbers. Mathematical quick calculation methods are divided into Jinhua quick calculation, Wei quick calculation, historical quick calculation and "swallowing gold in the sleeve" created by the ancients. Wei was brilliant since he was a child, and there were many unknown legends in primary school. One day, a math teacher learned from somewhere that Xiao Wei was very talented in the speed of digital calculation.

In order to be confirmed, he personally worked out an arithmetic problem of "1+2+3+4+-+ 1000" and asked Xiao Wei Wu De to work out an accurate answer in half an hour. As a result, Xiao Wei Wu De gave the correct answer in less than five minutes: "500500". Hearing this, the teacher was dumbfounded at once. He can't believe that Wei Dewei has such a fast calculation speed.

It turns out that Xiao Wei Wu De did not accumulate one by one according to the traditional method, but picked up a pen and kept drawing on the paper. Finally, the calculated natural numbers of "1+2+3+4+-+ 1000" are arranged in a trapezoid, and then with the help of the elementary trapezoidal area formula S = (a+b) ÷ 2.

The mantissa "1000" is the base length of the trapezoidal area, and the number "1000" is the height of the trapezoidal area (the actual height of the trapezoid is 999).