Chapter 61: The Nine-Nine Rhyme, and Mu Ying is Digging a Pit

Baoyuan Inn.

After taking a bath to wash away the exhaustion of the journey, Gu Zhengchen instructed Gu Cheng to order some wine and dishes, and invited Liang Jiajun over.

Seeing Liang Jiajun looking somewhat constrained and ill at ease, Gu Zhengchen personally poured a cup of wine and handed it to him. "Elder Liang bestowed a great favor upon the Gu family, and Brother Liang took meticulous care of me all along the way. I, Zhengchen, keep all of this deeply in my heart and will never forget it."

Liang Jiajun already knew that Gu Zhengchen would move out of the inn tomorrow to stay temporarily at the Mu Residence until assuming his post in Jurong. He made no secret of his envy. "I never imagined you would have such great fortune. In the future, when you sit high in the ministries, you must pull me along."

Gu Zhengchen raised his cup and smiled. "No matter what, I am still a magistrate of the seventh rank, stationed outside Jinling. On the contrary, Brother Liang, you are in the Imperial Academy with widespread connections, and your future is promising."

Liang Jiajun nodded.

Gu Zhengchen was right, and Liang Jiajun was clear-headed. No matter how prominent he was right now, and no matter how well he befriended people in Jinling, he was not an official of Jinling. Even if others wanted to promote him, it would not be easy.

As for the Imperial Academy, it had become particularly important following the suspension of the imperial examinations. The imperial court would select more personnel for officialdom from here. As an assistant instructor of the Imperial Academy, if he could educate a few students who rose to the ranks of vice ministers or ministers, relying on the teacher-student bond, he might well achieve rapid advancement in the future.

After a cup of wine, Liang Jiajun refilled his cup and looked at Gu Zhengchen. "As it happens, Uncle Kai has already helped me find a residence, and I can move in tomorrow. Parting today, we shall meet again as old friends. I wish Junior Brother Gu a splendid future and a lofty official seat!"

Gu Zhengchen raised his cup. "I wish Brother Liang peach and plum blossoms filling the world, and an early entry into the imperial court."

The banquet came to an end, and people departed in all directions.

Early the next morning, Liang Jiajun moved out first, and Gu Zhengchen watched him leave. Not long after, Zhang Pei, a guard from the Mu Residence, arrived at the inn with men to escort Gu Zhengchen and his two servants to the Mu Residence.

The steward Xie Fang settled Gu Zhengchen and the others in the west wing rooms, and after everything was properly arranged, reported back to Lady Feng.

"Scholar Gu likes to eat fish, so arrange for the back kitchen to prepare more over the next few days. He is an old friend of the master, so we cannot break the rules."

Lady Feng was Mu Ying's principal wife and Mu Chun's mother. Kind-hearted and knowing that Mu Ying had been busy with military affairs over the past two days while Mu Chun and Mu Sheng were too young to host guests, she personally inquired and instructed the steward to entertain them well without any negligence.

"Rest assured, Milady." Xie Fang agreed.

Martial Arts Practice Ground.

Gu Zhengchen resumed his training, gritting his teeth to persevere. For several days running, his whole body had been aching severely, but he could neither give up nor interrupt at this moment.

Zhang Pei watched the dedicated Gu Zhengchen, a trace of admiration welling up in his eyes.

He was a scholar, inherently delicate and frail, yet his bones revealed an unyielding drive. It seemed as though a powerful force was supporting him; even when exhausted to the extreme, he neither cried out in fatigue nor rested!

No one supervised him here, no one urged him on. He relied entirely on self-discipline and willpower to train alone! Such a person understood what he wanted and was willing to give his utmost effort for the desired result!

He was no ordinary scholar!

"So you are the one who snatched my younger brother's bow and sword?"

Gu Zhengchen looked over. What a handsome young boy, early in his teens with fair skin, bright eyes, and an innocent expression, holding a long spear in his hands.

"You made my younger brother cry, and I want you to apologize."

Mu Chun pointed his spear at Gu Zhengchen.

Gu Zhengchen looked at the guard Zhang Pei, only to find that this fellow was staring at the floating clouds and shifting dogs without sparing him a single glance.

"To correct you, I haven't even seen your younger brother, so how could I possibly snatch his bow and sword? The one who gave the order was your father, and the ones who took action were Wuxun and Zhang Pei. Neither mastermind nor accomplice falls upon me. You ask me for an apology; wouldn't that be confusing right and wrong, blurring black and white, and wronging an innocent person?"

Seeing the sandbags removed, Gu Zhengchen dropped them onto the ground.

Mu Chun looked at Zhang Pei. "Is what he said true?"

Zhang Pei thought about it; it seemed there was nothing wrong with that.

Seeing Zhang Pei nod, Mu Chun withdrew the long spear in some frustration, suddenly felt something was amiss, and pointed at Gu Zhengchen again. "But all of this started because of you. You are the ultimate culprit!"

Gu Zhengchen burst into hearty laughter and clapped in praise. "I can tell you are quite clever."

"That goes without saying. The teacher always praises my cleverness." Mu Chun lifted his small chin, full of pride.

Gu Zhengchen nodded, looked toward the pavilion not far away, and spoke. "Since you are so clever, you must be a gentleman. I am a scholar; if you want to vent your brother's anger, shouldn't you use a scholar's method?"

"No problem! If you lose, you must apologize to my brother." Mu Chun agreed without hesitation.

Gu Zhengchen nodded slightly. "If you lose, don't blame me for snatching your sword as well."

"I certainly won't believe you can win." Mu Chun was extremely confident.

Gu Zhengchen pointed at the pavilion. "As long as you can accurately measure the height of that pavilion, I will apologize to your brother. How about it?"

Mu Chun turned to look. That pavilion was a summer retreat specifically built by his father Mu Ying; standing atop it, one could overlook the entire courtyard of the Mu Residence.

"What is so difficult about this?"

Mu Chun agreed outright and looked at Zhang Pei. "You, climb up and see how high it is..."

Zhang Pei's eyes widened. *My young master, this is a contest between the two of you, there is no need to drag me into it. Besides, I cannot climb to the very top either.*

Half an hour later, Mu Chun was sweating profusely.

*Why is it that the rulers at home are only three feet long? Why couldn't they make one several丈 long? Why on earth did they build a roof when they constructed this wretched pavilion, and why did they install a finial on top, preventing me from measuring it? And the ladders too—why not make them taller? They are all wretchedly short ladders!*

Mu Chun was furious, wishing he could tear the pavilion down to the ground and measure its height piece by piece.

Gu Zhengchen was leisurely sipping tea, watching Mu Chun running up and down, busy with this and that. Hearing footsteps behind him, he turned around and saw that Mu Ying had arrived, so he stood up and cupped his fists. "Military Commissioner Mu has arrived."

"What is he doing?"

After returning the salute, Mu Ying watched his son throwing a rope up the pavilion, with a small stone tied to one end of the rope.

Gu Zhengchen explained the situation.

Mu Ying laughed heartily. "To bully the eldest young master of the Mu family, you must be the very first."

Gu Zhengchen shook his head, his expression turning serious. "I merely wanted to use this method to tell Young Master Mu Chun that solving problems requires attention to method. With the wrong method, one exerts twice the effort for half the result. With the right method, one achieves twice the result with half the effort."

Mu Ying restrained his smile and looked at Gu Zhengchen. "Paying attention to method—is this the origin of your life-saving techniques and body-forging techniques?"

Gu Zhengchen remained silent.

Mu Ying understood.

A problem was like a door; some doors had locks, and one needed to find the right key to open them.

Mu Chun was deeply frustrated, completely unable to measure the precise height. Seeing his father arrive, he felt extremely aggrieved. "Father, I am being bullied. This simply isn't something that can be done..."

Mu Ying placated Mu Chun and looked at Gu Zhengchen. "State your method, so that my son may be convinced of his defeat."

Gu Zhengchen looked at the shadow of the pavilion, then at Mu Chun's shadow, and said with a smile, "This matter is actually quite simple. The relationship between the height of the pavilion and the length of its shadow is identical to the relationship between a person's height and the length of their shadow. Divide one's own height by the length of one's shadow, and then multiply by the length of the pavilion's shadow to obtain its height."

"You should be familiar with the *Nine-Nine Rhyme*: 'One-nine, two-nine, hands stay in sleeves; three-nine, twenty-seven, horns blow on the fence; four-nine, thirty-six, sleeping at night like frost on twigs; five-nine, forty-five, the sun opens the gates...' All the way to 'nine-nine, eighty-one, plows and harrows come out together.' As recorded in *The Mathematical Classic of Sun Zi*, the method of division is precisely the opposite of multiplication. Your tutor should have taught you some of these calculation methods as well."

"In all things under heaven, there are always laws to be found and methods to be relied upon. In the words of the sages, it is to investigate things to attain knowledge, reaching the ultimate source. You are still young, but you must remember: there are no insoluble problems, only methods that have not been correctly found. Isn't that so, Military Commissioner Mu?"

Mu Ying nodded solemnly, looked at Mu Chun, and said with stern dignity, "Still not paying respects to your teacher!"

Mu Chun remembered the lesson and bowed deeply. "This disciple has been instructed."

Gu Zhengchen smiled and said, "Actually, there are many ways to know the height of this tower. You could even ask the craftsmen who built it; every structure has its standards and regulations. However, sometimes people need to rely on their own wisdom to solve difficult problems."

Mu Chun nodded repeatedly. "If the teacher does not disdain it, could you explain the *Nine-Nine Rhyme* and the principles of multiplication and division in detail? Although Master Wang in the estate teaches some, I do not understand them very well."

Gu Zhengchen understood that as the scion of a military family, one might not necessarily be literate, but basic arithmetic had to be mastered. The amount of logistics, the number of soldiers, distance, and time all relied on the art of calculation.

However, Mu Chun was still young, only eleven years old this year.

Gu Zhengchen readily agreed. "Then let us begin with the *Nine-Nine Rhyme*. As early as the Spring and Autumn and Warring States periods, people began using the Nine-Nine Rhyme to calculate. People back then started from 'nine-nines are eighty-one' down to 'two-twos are four', and later down to 'one-one is one', the way of multiplication..."

Mu Ying stood aside, listening with rapt attention.

Compared to Master Wang invited into the estate, Gu Zhengchen seemed much better suited to be a teacher. He appeared deeply proficient in the art of calculation, casually sketching on the ground to simplify complex arithmetic. The mathematical principles he expounded differed from classics like *The Nine Chapters on the Mathematical Art*, yet implicitly coincided with them.

"Milady's husband." Wuxun walked up to Mu Ying's side and called out in a low voice.

Seeing Wuxun's solemn expression, Mu Ying stepped aside to question him. "What is it?"

Wuxun reported in a low voice, "The Emperor has issued an imperial oral edict, instructing the Grand Military Commission to resettle the over two thousand two hundred Tatar officers and soldiers captured last month within the five counties of Liuhe, Jurong, Jiangpu, and others in Yingtian Prefecture, changing their barbarian surnames and reducing them to obedient citizens."

Mu Ying frowned slightly, feeling somewhat worried. "Liuhe, Jurong, Jiangpu and other places are right near Jinling. If they rebel, they could enter Jinling before dusk even if they started at dawn! Wouldn't that be dangerous?"

Wuxun dared not speak. This was the command of the Hongwu Emperor, Zhu Yuanzhou.

Mu Ying waved his hand. "Since the Emperor has issued the oral edict, we shall carry it out accordingly. Only, this way, it is likely to cause hardship for the local commoners. Wait, did you say Jurong County is also among them?"

"Yes."

"Jurong, you say?"

Mu Ying looked at Gu Zhengchen, who was still explaining problems to Mu Chun, and slowly said, "The Grand Military Commission cannot violate the imperial will, but we can coordinate and adjust the distribution numbers. Tell me, if we were to resettle some twelve hundred people in Jurong..."

Wuxun's Adam's apple bobbed, his expression turning somewhat unsightly as he glanced at Gu Zhengchen in the distance. "Milady's husband, once these people revolt, he might die..."