Chapter Thirty-Seven: The Application of Geometry

After Yun Hao shouted, he stepped in front of Madam Zhao. He could not allow his mother to be harmed; after three months together, Yun Hao already regarded this woman as his own mother. If she suffered even the slightest injury, Yun Hao would wipe out Wu Yuanshuang’s entire family, regardless of whether his sister was Wu Zetian.

“So? Boy, do you dare to compete with me?” Wu Yuanshuang pressed arrogantly when he saw Yun Hao step forward. He was convinced that the boy had just tried to fool him—how could he lose to a mere child in a contest of knowledge? Ridiculous! All his years of diligent study were not for nothing.

“How do you want to compete?” Yun Hao retorted angrily. This bastard really doesn’t know when to quit!

Wu Yuanshuang was momentarily taken aback; he hadn’t expected Yun Hao to accept the challenge. Now, how to compete became a question. He turned to look at his father and Zhang Wenzhong for guidance.

Zhang Wenzhong replied unhurriedly, “That’s easy. Didn’t you say we can measure the height of a mountain with its shadow, and the depth of the Yellow River with a bucket of water? Let’s do it this way: if you can determine the height of this pole and the weight of this millstone, you win. If so, I will strictly reprimand Yuanshuang for his rudeness, and compensate you and your mother with ten taels of silver. How about it?”

Zhang Wenzhong had already devised a plan. Measuring Mount Tai and the Yellow River was impossible; even if someone attempted it, any answer could be given without proof. But the height of this pole and the weight of that millstone could be determined—both were tangible objects, measurable. Even if the boy spouted nonsense, punishing him would be justified, and the neighbors wouldn’t say they were bullying a helpless widow and her child.

In truth, Zhang Wenzhong thought the boy was exaggerating. How could a child of just a few years possess such uncanny abilities? But if he did, Zhang Wenzhong wouldn’t hesitate to revere him.

Yun Hao followed Zhang Wenzhong’s gesture and indeed saw, a few steps away, a bamboo pole propping up a shelter. At its base was a millstone, about a foot in diameter.

“A gentleman’s word is his bond!”

“Once spoken, it cannot be taken back!”

A large and a small palm slapped together—a formal contract in the Sui dynasty. Especially for an agreement made in public; should either party renege, they would be scorned throughout the city, unable to hold their head up again! Zhang Wenzhong, treating this as a jest, clapped hands with Yun Hao, then stroked his beard and gave Wu Shihuo a wry smile. All this was for Wu Yuanshuang’s sake—he had watched the boy grow up and cared for him deeply. Besides, his niece Zhang Miaoke was involved in today’s affair.

Wu Shihuo returned the wry smile. Today’s events were absurd: the famed physician Zhang Wenzhong was gambling with a child in public. Should word spread, it would certainly become a laughingstock.

Wu Yuanshuang sneered at Yun Hao, eager to see how the boy would manage. If he failed, well! He would make the boy suffer, beat him until even his own mother would not recognize him—otherwise, he would not be worthy of his surname.

As for the onlookers, they all harbored curiosity about the boy. Could the height of a pole and the weight of a millstone really be calculated? The crowd buzzed with speculation, livelier than a festival. More people kept arriving to watch; after all, in this land, there was nothing the people enjoyed more than a good spectacle.

“I need a large wooden bucket filled with water, a rope, and a measuring stick!” Yun Hao called to Zhang Wenzhong after inspecting the pole and the millstone.

He would use the method of measuring density to determine mass, and the Pythagorean theorem to find the height. He had learned these in middle school—he might not have attended high school, but compared to these fools of the Sui and Tang, he was a force to be reckoned with. Yun Hao was confident; while he had not excelled in school, he had always passed physics and geometry.

Zhang Wenzhong looked troubled; he certainly hadn’t brought along a ruler, rope, or bucket. At that moment, an old man who made dough figurines called out, “I have a rope! Can some neighbors provide the other items? In my fifty years, I’ve never heard of anyone calculating such things. Today, I must witness it for myself!”

The old dough figurine vendor couldn’t wait to see Yun Hao make a fool of himself, and immediately began gathering the items. If Yun Hao failed or couldn’t work it out, he’d be the first to join in when the boy was beaten.

Who among the crowd didn’t want to see something novel? One contributed a bucket, another fetched water, someone found a ruler. In no time, all the items Yun Hao requested were assembled. All eyes were fixed on him, waiting to see what method he would use. If he made a mockery of things, a beating would be the least of his troubles.

“Thank you, neighbors, for your help. Wu Yuanshuang is grateful. Since I’m using your possessions, I will pay for anything used and compensate for any damages,” Wu Yuanshuang called out, showing off once again. His words won praise from the crowd, especially those who had lent items, who now saw Wu Yuanshuang as a model youth and urged their own sons to learn from his example.

Wu Yuanshuang, basking in the compliments, cupped his hands in thanks, stealing glances at his cousin Zhang Miaoke. Seeing her cheeks flushed and her eyes sparkling with admiration, his spirits soared. In his good mood, he decided he’d go easy on Yun Hao later—breaking just one leg would suffice.

“Let’s measure the bamboo pole first!” Yun Hao ignored Wu Yuanshuang’s smugness, picked up the rope, and began his calculations, drawing figures on the ground. Before long, he stood up and announced to the crowd, “I hadn’t measured the length of the pole before, but now I know it is eight feet nine inches. Esteemed elder, you are known for your fairness. Please measure the pole and confirm its height!”

He respectfully invited Zhang Wenzhong to verify the result.

Zhang Wenzhong was stunned by how quickly the boy had calculated the answer. Glancing at the strange scribbles on the ground, he couldn’t make sense of them. He signaled a servant to measure the pole, who, with two others, got to work. After measuring, the servant looked at Zhang Wenzhong with a troubled expression.

Both Zhang Wenzhong and Wu Shihuo’s faces changed; just from the servant’s look, they could tell the boy was right!

“Don’t look at me—just speak the truth!” With so many people watching, Zhang Wenzhong knew he could not falsify the result; any attempt would only invite ridicule.

“Eight feet, nine inches…” The servant forced out the answer, and the crowd erupted in astonishment. The buzz of voices sounded like a swarm of ten thousand flies.

Wu Yuanshuang exclaimed in disbelief, “How is that possible?” He rushed forward, seized the ruler and rope, and measured for himself. When he finished, he collapsed to the ground in shock.