Start with a photographic memory and build a memory palace

Chapter 18: Duel with Li Chunfeng

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"Your name is Wu Wen, what is your courtesy name?"

Hearing Wei Zheng's question, Wu Wen shook his head slightly.

"No?"

"Then you must behave well. Maybe one day His Highness will personally grant you a courtesy name. Then you will bring honor to your family and be remembered in history."

Hearing this, Wu Wen chuckled and thought to himself that he did not have such extravagant hope. He just hoped that he would not be implicated after the Xuanwu Gate Incident.

"You haven't told me where you are from or where you live?"

"I am from Zhujia Village, Wannian County, outside Chang'an City."

"Oh!" Wei Zheng nodded slightly.

"Now that you have entered the Eastern Palace, it will be inconvenient for you to travel back and forth. So, I will arrange a residence for you outside the palace, and you can live there on weekdays, okay?"

"Thank you so much, Wei Xima!" Wu Wen bowed and expressed his gratitude.

Wei Zheng waved his hand slightly, as if this was just a trivial matter.

Continue to take Wu Wen to visit the library.

In a corner that Wu Wen didn't notice, a figure disappeared quietly, then left the East Palace and went to investigate his identity information.

The two came to the top floor of the fourth floor of the library, which was a small attic.

There was an instrument in the center of the attic.

Wu Wen stopped to observe and felt that this thing looked like a celestial globe, but also a little bit different.

There were desks placed right in front of him, and a middle-aged scholar was lying in front of the desks, concentrating on writing something. Even when Wu Wen and Wei Zheng approached, he seemed not to notice and continued to be busy with his own work.

Wei Zheng introduced Wu Wen, "This man is a doctor of mathematics in the Prince's Palace, his name is Li Chunfeng."

"What did you say his name was?" Wu Wen asked in surprise.

"Li Chunfeng, how come you know him?" Wei Zheng asked puzzledly.

Wu Wen shook his head: "I don't know him, but I've heard of his reputation. He's a very powerful person."

He didn't expect that he would meet the legendary figure here.

In some of the familiar stories he knew, Li Chunfeng was simply a god-like figure. Not only was he proficient in astronomy and arithmetic, but he also mastered the magical ability of divination and deduction. The "Tuibei Tu" he and Yuan Tiangang created together was even more magical.

The conversation between Wu Wen and Wei Zheng disturbed Li Chunfeng who was thinking.

He looked up at the two of them and saw Wu Wen, a stranger he had never seen before. He then asked Wei Zheng, "Wei Xima, who is this person?"

"His name is Wu Wen, and His Highness asked him to come here to study."

Hearing the answer, Li Chunfeng showed a strange expression on his face. Since the prince allowed him to study here, this person must be no ordinary person.

Therefore, he immediately became interested in Wu Wen and asked, "What are you good at?"

"My family is poor, and I haven't read many books, but I'm pretty good at arithmetic."

"Oh?"

Hearing this, Li Chunfeng became more interested in Wu Wen and directly asked him to test him further.

“Question: There is an object, whose number is unknown. If you count three by three, there are two left. If you count five by five, there are three. If you count seven by seven, there are two left. How many of these objects are there?”

As soon as this question was asked, Wei Zheng turned to look at Wu Wen, looking forward to his performance.

This is a typical "remainder theorem" question, which Wu Wen had learned in elementary school. He lowered his head and pondered, and the calculation process quickly emerged in his mind.

First, let the number be x, then list three congruence equations according to the conditions of the question, then use the properties of congruence equations to combine and simplify them, and finally get the answer through mental arithmetic.

After a while, Wu Wen said confidently: "The number should be twenty-three."

When Li Chunfeng heard this, a hint of surprise flashed in his eyes. He didn't expect Wu Wen to be able to solve the problem so quickly, and the answer was completely correct.

"Okay, good! Listen to the questions again!"

"Now there is a wall eight feet thick, and two rats are crossing it. The big rat grows one foot a day, and the small rat also grows one foot a day. The big rat doubles its thickness, and the small rat halves its thickness. When will they meet again?"

The meaning of this question is: There is a wall that is eight feet thick. Two mice start digging holes from both sides of the wall at the same time. The rat digs one foot a day, and the mouse also digs one foot a day. However, the length of the hole dug by the rat will double every day, while the length of the hole dug by the mouse will halve every day. How many days will it take for the two mice to meet?

The difficulty has increased!
But this still does not pose a problem for Wu Wen.

This was a complex arithmetic problem involving the summation and intersection of geometric series. To him, it was at most a junior high school math problem.

He picked up the pen and a blank piece of paper on the table and began to write and draw on them.

First, assume that the length of the holes made by rats every day is a geometric sequence, with the first term being 1 and the common ratio being 2; the length of the holes made by mice every day is also a geometric sequence, but with the first term being 1 and the common ratio being 0.5.

Then, based on the summation formula of the geometric progression, the total length of the holes dug by rats and mice at the end of each day was calculated.

Next, set up an equation to express that the total length of the holes made by rats and mice is equal to the thickness of the wall, which is 8 feet. Then solve this equation to find the number of days until the encounter.

After some complicated calculations, Wu Wen finally got the answer.

"The two mice will meet on the fourth day."

When Li Chunfeng heard this, a hint of surprise and admiration flashed in his eyes.

However, Wu Wen's performance also aroused his competitive spirit.

"Ask again!"

"There is a solar eclipse now. It starts at the first quarter of the morning and ends at the third quarter of the evening. How long will the eclipse last, and how much area of the sun and moon will be covered by the eclipse?"

When this question came up, Wei Zheng couldn't help but frown slightly.

This question involves the observation of a solar eclipse, the calculation of time, and the estimation of the areas of the sun and the moon, and requires profound knowledge of astronomy and geography to answer.

Li Chunfeng is competitive, and Wu Wen is no exception.

How could he, a top student who had studied advanced mathematics in modern times, be willing to be outdone by an ancient person?
Although he had never directly observed a solar eclipse, he understood basic astronomy and knew that a solar eclipse is an astronomical phenomenon caused by the moon moving between the sun and the earth and blocking the sun's rays.

As for the duration of the solar eclipse, he could use modern time calculation methods based on the start and end times given in the question.

As for the area of the sun and moon covered by the solar eclipse, he needed to estimate it based on the size and distance of the sun and moon and the type of solar eclipse, such as total eclipse or partial eclipse.

Although the question did not give the specific type of solar eclipse, Wu Wen judged based on common sense that this was most likely a partial eclipse, because a total eclipse usually lasts shorter and completely blocks the sun.

He picked up the pen again, sat down at the desk, and began to calculate seriously.

Li Chunfeng and Wei Zheng on the side also remained quiet and watched quietly.

"The duration of the solar eclipse is from the first quarter of the chen hour to the third quarter of the si hour, a total of one hour and three quarters.

As for the area of the sun and moon covered by the solar eclipse, since the specific type of solar eclipse is not given, I assume it is a partial eclipse. Based on the size and distance of the sun and moon, I estimate that the area covered by the solar eclipse is about one-third of the area of the sun. "

clap clap ~
After hearing Wu Wen's answer, Wei Zheng clapped his hands in praise.

When Li Chunfeng looked at him, there was more than just admiration in his eyes, it was as if he saw a like-minded person.

……

(End of this chapter)