Su Mansion.

Inside Old Su's study.

At this very moment.

A small but vigorous old man sat on a chair, his sharp eyes like an eagle's were locked intensely on Wang Lin who sat opposite him.

As if the next second, beams of light would shoot out from his eyes and turn Wang Lin into dust with a "biu":

"You are Wang Lin?"

Xu Yun rubbed the back of his neck and sighed:

"That's me, the humble one."

Hearing this, the old man immediately pulled out a letter.

Slam!

The old man flung his wrist and smacked it heavily onto the table:

"Did you write this letter?"

Xu Yun opened his mouth, wanting to say something cheeky like 'The master wrote this letter.'

But considering he might get a beating if he said that, and his character isn't like Wang Qiang, that joker, he simply sighed and said:

"That's right."

"....."

The old man frowned and said in a deep voice:

"Wang Lin, though this is our first meeting, you don't seem to be that treacherous of a person, and your calculations are far above average. Why do you like to cut chapters so much?

I know a chapter-cutter... ahem, a chapter-ender, and now there's probably a mound a meter high on his grave."

This question was one Xu Yun had been asked countless times in his past life, so he replied reflexively without thinking:

"No particular reason, just got used to it."

The old man:

"???"

He then took a deep breath, suppressed his anger, and said resolutely:

"Wang Lin, I've already personally come to Bianjing, shouldn't you show me the rest of the content?"

This time Xu Yun was straightforward, taking out a piece of paper from his body.

Unfolding it, laying it flat.

Pressing down on one corner, he pushed it in front of the elder... which was Jia Xian:

"Mr. Tongyu, the rest of the content is all here, please take a look."

Jia Xian's eyes lit up instantly.

He eagerly took the paper and started reading it seriously:

"....Upon completion, one hundred and thirty-two thousand eight hundred and sixty-seven units, calculation steps as follows..."

".....Then one proceeds with the next divisor twenty, entering solid together three hundred and forty, multiply solid into mass, total forty-three thousand and two hundred square feet."

"....Then multiply again entering solid together three hundred and sixty... its mass one, solid two, remainder three downwards, as before."

Jia Xian analyzed as he read, the entire process without using any paper, pen, or tools, completely relying on mental arithmetic!

"....The upper divisor of the third position yields three, multiply again entering solid, total three hundred and sixty-three, multiply solid into mass, total forty-four thousand two hundred and eighty-nine....."

".....Use the upper divisor three to divide the actual, exactly, obtaining...."

"The number of one side of the cube."

After reading the last sentence.

Jia Xian couldn't help but close his eyes, frowning slightly, as if verifying the result.

After about a minute or so.

This seemingly hot-tempered little old man slowly opened his eyes, exhaled a breath of impure air, and looked at Xu Yun with a complicated expression:

"No errors in the calculation text, yet the method for finding solid in the Nine Chapters now has a third solution."

Nine Chapters on the Art of Mathematics.

This is an ancient book even modern elementary students have heard of.

But many have only heard of its name, not knowing why it's called the Nine Chapters on the Art of Mathematics.

The reason is simple.

Because it is composed of nine chapters...

That's right, it's that simple...

These nine chapters are Field Measurement, Millet and Rice, Disproportion, Lesser Width, Functional Operations, Equitable Distribution, Surplus and Deficiency, Solving Systems of Linear Equations, and Pythagorean Theorem.

Among them, in the chapter 'Lesser Width', the most famous should be the process of finding the cube root of 1860867. (Note: previously someone actually asked me which person the Lesser Width chapter is about...)

Until the year 1100 AD, the ancients had only proposed two methods for extracting cube roots.

The method proposed by Xu Yun, however, was one that had never been discovered before.....

The third solution!

Similarly.

This was also a mystery that Jia Xian had always wanted to solve in the first half of his life.

But unfortunately.....

Human energy is limited.

After discovering the secret of triangles, Jia Xian could only regrettably give up on solving the problem of cube roots, devoting all his thoughts to the field of triangles.

This is like some online writers in later generations.

Originally writing a book with one to two thousand subscribers, but suddenly an unexpected hit came out under a pseudonym, so they helplessly abandoned the former to write the latter.

Of course.

Xu Yun definitely wouldn't do such a thing, as most of his books were only followed up upon being banned.

.....This is truly a sad story.

Then Jia Xian took another deep breath, pointing to a corner of the envelope, and asked Xu Yun:

"Wang Lin, what do the symbols in this corner of the letter mean?"

Xu Yun leaned over, took a few glances, and explained:

"You mean these? These are Arabic numerals."

"Arabic numerals?"

Xu Yun nodded and continued:

"They're symbols invented by the people of the Western Regions, corresponding to Huaxia's one, two, three, four, and make writing somewhat simpler. Mr. Tongyu could also give them a try."

Arabic numerals, unlike Yang Hui's Triangle, were indeed invented by ancient Indians and weren't an overlooked ancient achievement of Huaxia.

So Xu Yun didn't deliberately claim them as his own, since he's no thief.

Currently, Huaxia frequently uses a small tool called chips for calculations.

Somewhat similar to chopsticks of later generations, each about ten to twenty centimeters in length, they are also called counting rods.

When calculating.

One simply has to arrange these chopsticks in different formations to represent various numbers for calculations.

Moreover, sometimes if there were no calculation chips, one would use it.....

Ahem.

In short.

Although this way is a bit more convenient than paper calculations, it is still somewhat cumbersome compared to Arabic numerals.

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