Wang Ou thought it was interesting, so he said: "Can this set of symbols teach the slave family?"

"Absolutely." Li Mu squatted down, picked up a branch on the ground, wrote down nine numbers from 1 to 9, and then wrote 0 in the space behind 9. Wang Ou also squatted next to him and watched seriously.

"Starting from 1 and going all the way to 9, it corresponds to one to nine, and the next 0 is zero. If you want to record a number greater than nine, add one digit in front of it. Li Mu wrote a '10' in the following line to explain: "The position of this 0 represents one. The first digit represents ten. Now one here is O, which means no. Here is 1, which means a ten, which is 10. ”

Li Mu himself didn't think he had explained much, but Wang Ou actually understood. He also took a branch and wrote a 15 on the ground, saying, "Does this mean fifteen?" One ten, five one. ”

"Yes, yes, yes!" Li Mu nodded vigorously, and secretly said in his heart, she really deserves to be the daughter of a famous family, and she is really very smart. Li Mu took out the Arabic numerals, which he intended to use. Since Wang Ou is curious and so smart, it is of course only fitting for her to be his first student.

Li Mu wrote '+''-'''×'÷'=' five symbols on the ground, and said: "When I was in Dingxiang, I read the "Zhou Ji Sutra" brought by my righteous brother Li Siwen. At the time, after reading it, I found it cumbersome. The arithmetic described in it, to calculate a simple problem, to write several lines, is too troublesome for me. ”

"This matter has always been in my heart, and I thought that after arriving in Chang'an, I would be able to find a solution. When I lived in my father's house, I asked several old account rooms, and they all used arithmetic methods, and later I worked in the Ministry of Industry, and found that the craftsmen who worked did not even know how to use algorithms, and they relied on the experience passed down from generation to generation to deal with problems, and they themselves could not tell how to calculate. ”

Li Mu sighed: "I think about it, it's not a way to go on like this. So I invented this set of symbols for counting. Li Mu pointed to the ground and said, "After counting is feasible, I have repeated countless experiments, invented these five symbols, and finally completed a set of my own algorithms. I call this the Four Algorithms. ”

"Four arithmetic? An algorithm you invented yourself? Wang Ou's tone was full of incredulity, she had studied arithmetic, and she had learned more than one sutra. Taiyuan Wang's collection of books is rich, Wang Ou has read since he was a child, and has studied "Zhou Ji Sutra", "Nine Chapters of Arithmetic", "Island Sutra", her arithmetic level, even if she goes to participate in the imperial examination of the 'Ming Arithmetic' subject, she can easily rank among the best, so she knows the profundity of arithmetic.

The existing scriptures are all the truths that can only be derived from the ability of the sages to spend their lives and summarize the experience of their predecessors. And how old is Li Mucai, who even boasted that he had invented a set of algorithms in Haikou?

Wang Ou was a little unconvinced.

Li Mu heard it, and felt a little unhappy. If he talked about it, he didn't dare to boast, and when it came to mathematics and numbers, he still dared to say that he was proficient. In his previous life, he did data balancing and worked with numbers every day. Sometimes, in order to correct a skill formula, I have to get up in the middle of the night and work overtime. He is very sensitive to numbers.

Even aside from his job, he is a college graduate. If you pass the calculus, can you still do the four arithmetic?

Li Mu smoothed the handwriting on the ground with his hand and said, "These five symbols represent addition, subtraction, multiplication and division, five meanings. ”

"Addition and subtraction are very simple, and they are recorded in the Zhou Ji Sutra, but multiplication and division, I found a simple calculation method."

"There is a 'Song of Nine Causes' in the Zhou Ji Sutra, which records a simple multiplication formula. Such as two-two, four-nine-nine-eighty-one, etc. But it can only perform a few operations, and if it is a larger number, it will not be able to do it. But with my symbol, plus my algorithm, I can calculate any number of sizes. ”

Li Mu wrote 23X18 on the ground, explaining to Wang Ou: "For example, this twenty-three times eighteen, the number at both ends of the symbol, I named it the factor according to the nine cause song, we can use the unit of the second factor 8, first multiply the unit of the first factor 3, get 24, we write it down, and then use 8 to multiply the ten place of the first factor 2, to get 16, because this 2 is in the ten place, so we write 16 in front, so we get a hundred, two tens, one by one." We add the two digits of ten to get 8, which gives us 184. ”

Li Mu wrote down 184, and then continued to write below: "Then we use the ten digit 1 of the second factor, and multiply it again according to the method just now, because this 1 is the ten digit, so we get 23 tens, add 18 with 23, get 41, and add your 4 to get 414." How, isn't it easy? ”

Don't look at what Li Mu said cumbersomely, but for the level of mathematics in the Tang Dynasty, this is already very fast. So much so that Wang Ou couldn't believe that the numbers calculated by Li Mu were correct, he kept these two numbers in his heart, and planned to use the method he had learned to calculate again when he got home to verify whether Li Mu's algorithm was correct.

"Coming to this division, division can be seen as the inverse of multiplication. Just now we get 23X18=414, then we count 414 divided by 18. From the high division of the dividend, the divisor is a few digits, just look at the first few digits of the dividend, if it is not enough to divide, you have to look at one more digit, the resulting number, I call it 'quotient', and the remaining number is called 'remainder'. The remainder of each division must be smaller than the divisor, and if the highest digit of the quotient is not enough for quotient 1, write 0 on which digit ......"

Li Mu had tried very hard to make it simple and easy to understand, but he had long forgotten how the old dean taught him when he was learning addition, subtraction, multiplication and division. Now that he has long practiced the instinct of mental arithmetic, these steps are almost ignored when he calculates, and there is really no way to make it simpler.

Crying and slugging a lot, Li Mu said himself a little confused, and looked at Wang Ou, who was squatting next to him and frowning and contemplative, and was very unsure whether she could understand it.

Wang Ou didn't speak for a long time, suddenly picked up a branch, wrote a 12X13 on the ground, and then calculated 156 step by step according to Li Mujiao's multiplication. According to the division of Pastoral Lee, divide 156 by 12 to get 13. Li Mu clapped his hands excitedly, grabbed Wang Ou's arm, and said excitedly: "You are so smart!" You understand what I'm talking about! That's amazing! ”

Wang Ou was grabbed by Li Mu's arm, and subconsciously wanted to retract, but seeing Li Mu's excited appearance, a trace of hesitation flashed in his eyes, and he didn't do so. It was the first time that she was actively grabbed by a man's arm, and a strange feeling surged in her heart, but she was no longer an ignorant girl, she was not overly shy, but her cheeks were slightly red.

She used 12 times 13 because she had just brought in twelve cartloads of cloth yesterday, and each cart had thirteen pieces of cloth, and the result of one hundred and fifty-six was actually found out one by one. With this accurate answer, and then to verify Li Mu's algorithm, we can naturally know whether it is accurate or not.

The result surprised her, Li Mu's algorithm was so accurate and accurate. The seventeen-year-old man in front of him really invented an algorithm by himself. And it's so simple, you can use it almost without knowing any arithmetic, how the hell did he do it, such a big ability!

If there is really someone who is so genius here, then the people who study the scriptures in the world, won't it become a joke?

Wang Ou is not a person who is easy to get angry, but at this time, he can't help but want to ask for an explanation for the arithmetic scriptures he has learned for so many years when he was young. She pondered for a while, and suddenly remembered an unsolvable question in the "Qiu Jian Sutra" of the Northern Wei Dynasty that she had read, which was called 'Hundred Chickens Ask'. Since the book was written in the Northern Wei Dynasty, no one has been able to solve this problem for more than 300 years.

Wang Ou didn't expect Li Mu to be able to solve it, she just wanted to hit Li Mu and see how frustrated he looked. She didn't know why she suddenly had this bad taste, she clearly knew that she was not such a person. After seeing Li Mu's surprises, Xu was confused in his heart.

After making up his mind, Wang Ou said this 'Hundred Chickens Ask'.

"Master Hou, the slave family has also read the scriptures, and there is a question that the slave family has not solved so far, I wonder if you can solve this algorithm?"

Li Mu didn't know what Wang Ou's idea was, thinking that she was still not convinced by her four calculations, so she said, "You say, I'll try." ”

"There are roosters, which are worth five; The hen is one, it is worth three, and the chicken is three, and it is worth one. Buy 100 chickens for 100 dollars, and ask how many roosters, hens, and chickens are? ”

"Hmm...... Is this a problem? Li Mu pondered for a while, but he didn't feel the difficulty, he just felt strange, the level of mathematics in the Tang Dynasty had already begun to study the system of ternary indefinite equations?

Wang Ou saw Li Mu embarrassed, and his heart was overjoyed, finally stumped him!

"If it's too difficult, Master Hou shouldn't forget it, the slave family is just curious, this question is ancient and modern, ...... "Wang Ou wanted to say, how many arithmetic masters have not calculated this question, and it is not ashamed to calculate it, and the voice did not fall, only listened to Li Mudao: "Four roosters, eighteen hens, seventy-eight chickens, or male **, eleven hens, eighty-one chickens." Or twelve roosters, four hens, and eighty-four chickens! There are three answers! ”

"Huh?" Wang Ou was completely stunned, Li Mu not only said the answer, but also said three answers.

Seeing her stunned, Li Mu was proud in his heart, and said, "If you don't believe it, you can verify it." ”

Of course, Wang Ou wanted to verify, and it just so happened that Li Mu had just taught her multiplication, and it didn't take much time to verify. She only verified the first answer, and the calculation was indeed correct. Suddenly, I closed myself a little, looked at the numbers on the ground, and didn't make a sound for a long time.