From a slave to the Great Qian Martial Saint

"Another stone gate?"

Deep inside the cave, a huge round rock blocked the way.

There were no traps or mechanisms, not even a fork in the road, just a stone door similar to the Chilong Cave.

This stone door cannot be opened or destroyed unless activated by a mechanism, a fact that has already been verified in the Chilong Cave.

Looking at the stone door, Chen Shi's face gradually revealed a hint of excitement.

Since it's the same mechanism, it means that this place and the Chilong Cave share the same origin. Since they share the same origin, it means that this place is very likely the place where the array diagrams are stored.

As for how to open the stone door and get the array diagram inside, Chen Shi looked at the wall next to him.

"Exam questions?"

Although it is the same mechanism stone door, unlike the Chilong Cave, this door can be opened from the outside.

If this place cannot be opened, how will future generations retrieve the array diagrams inside?

Pearls are inlaid on the wall, and under the dim light, one can roughly see the surroundings. There is also an inscription on the wall.

"Solve the three problems and write the answers on the jade slab. If you answer all three correctly, the gate will open automatically. Remember, think carefully before answering; you only have one chance per problem."

It was quite unexpected that the test was on math problems.

Although mathematics existed in this world, it was not included in the imperial examinations and was rarely used in daily life. It could neither secure high-ranking official positions nor support a family, so it was regarded as a lowly skill and not valued by the world.

But that's just right.

When Chen Shi was young, he was more interested in arithmetic than in classics, history, philosophy, poetry, and prose, and often sought out mathematical texts to read. It was for this reason that his private tutor complained to his father, saying that he was neglecting his studies, and his mother urged him to drop out of school.

Chen Shi was too lazy to think about these old stories anymore, and looked up at the three arithmetic questions next to him.

Problem 1: There is an unknown number of objects. When counted in groups of three, there is a remainder of two; when counted in groups of five, there is a remainder of three; when counted in groups of seven, there is a remainder of two. How many objects are there?

"When you count in groups of three, there are two left over; when you count in groups of five, there are three left over; when you count in groups of seven, there are two left over..."

Breaking down the questions one by one, Chen Shi pondered for a moment before looking at the first question, a slight smile appearing on his lips.

This problem is quite brain-taxing when you actually solve it, but there's a seemingly clumsy but actually simpler way.

The remainder when counting fives is three. The possible values ​​for five-five are five, ten, fifteen, twenty, and so on. The remainder of three is eight, thirteen, eighteen, twenty-three, and so on...

Chen Shi listed these numbers and then used them to verify the other two conditions: when counted in groups of three, two remain; when counted in groups of seven, two remain.

"...Got it."

After only a few tries, the answer was found to be twenty-three.

Below the question was a jade slab. As instructed, Chen Shi stretched out his finger and wrote "twenty-three" on it.

The stone slab suddenly lit up, indicating that the question was answered correctly.

It doesn't seem too difficult.

Chen Shi smiled slightly and then looked at the second question.

Question 2: There is a pond one zhang square. Reeds grow in the center, rising one chi above the water. If the reeds are pulled to the bank, they will be level with the bank. What is the depth of the water?

"A pond is one zhang square. Reeds grow in the very center, extending one chi above the water. If you pull the reeds towards the bank, their tips will just touch the edge. How deep is the water...?"

Looking at the question, Chen Shi pondered for a moment, then his eyes lit up.

Unlike the previous question, this question doesn't allow you to list some alternative results and then try them one by one. Without the right method, it's difficult to solve.

Chen Shi, with his limited arithmetic skills, was not capable of solving this problem, but coincidentally, he had seen the algorithm for it before.

An elder surnamed Shang once mentioned in his own mathematical classic, "The method of numbers originates from the circle and the square, the circle originates from the square, and the square originates from the rectangle. Therefore, the angle of the rectangle is three, the length of the leg is four, and the corner of the longitude is five."

This problem is applicable to the formula "3-pythagorean theorem, 4-pythagorean theorem, 5-pythagorean theorem", so you can get the answer simply by matching the numbers.

"Got it."

After calculation, it was found that the reeds were thirteen feet long and one foot above the water, so the water depth was twelve feet.

After confirming that everything was correct, Chen Shi wrote "twelve feet" on the jade slab below.

Sure enough, the stone slab lit up, indicating the answer was correct.

Having solved two questions in a row, Chen Shi pressed on and immediately turned his attention to the third question.

Question 3: A transport vehicle, Cheng Chuan, can travel 70 li per day with an empty cart and 50 li per day with a loaded cart. It is carrying grain from Yongqiu to Wuxing, making three round trips every five days. How far is Yongqiu from Wuxing?

"To transport goods, an empty cart travels seventy li per day, and a loaded cart travels fifty li per day, transporting grain from Yongqiu to Wuxing. After five days and three round trips, what is the distance between Yongqiu and Wuxing?"

Looking at this question, Chen Shi couldn't help but frown. Compared to the previous two questions, this one was much more difficult.

Fortunately, although he had not yet found an answer, Chen Shi believed that he should be able to find it.

Frowning in thought, he slowly pieced together his thoughts...

About fifteen minutes later, the method gradually took shape in my mind.

"If we first calculate the time required to travel one mile round trip..."

Since he had no paper or pen at hand, Chen Shi used his finger to carve on the wall. The dragon scales scraped across the stone slab, making a hissing sound and leaving clear marks.

First, determine the number of days it takes for an empty cart to travel one mile and the number of days it takes for a loaded cart to travel one mile. Add the two together to get the number of days it takes to travel one mile round trip.

The journey took five days. The answer is: how many days did it take to travel one mile round trip?

"Got it"

After the performance, a number was obtained. Chen Shi smiled slightly and wrote it down directly on the bluestone slab.

Forty-eight li and one hundred and eighty-three steps!

The next moment, the third jade slab also lit up.

Boom!

All three jade slabs lit up, all three questions were answered correctly, and the next moment, with a roar, the stone door in front of them slowly opened.

It opened as expected.

Chen Shi looked excitedly into the stone gate.

Surprisingly, it wasn't a very large space, even smaller than the previous passage. However, the interior of the Chilong Cave, despite having the same stone door, was extremely spacious.

But that makes sense, since the Chilong Cave was used to seal off the Chilong, while this place is just for storing array diagrams.

It was only about four or five feet in diameter, and there was no decoration. On the stone slab, there was a chessboard.

It's not a real chessboard, but it looks similar to one.

"A battle formation!"

Chen Shi's eyes lit up, and he quickly walked over.

Just as he was about to reach out, he suddenly stopped, hesitated for a moment, then extended a foot-long knife and gently touched it. The chessboard wobbled slightly, but no mechanism was triggered.

"Looks like I was overthinking it."

Chen Shi smiled and then reached out to pick up the chessboard again.

It was about a foot wide, but it didn't have 19 lines in total. The chessboard was shrouded in mist, resembling a Bagua formation.

"There can be no mistake."

Looking at the arrangement of the eight trigrams above, Chen Shi was filled with excitement. This was the formation diagram of the Chilong Cave Formation.

With this array diagram, the Chilong Cave array can be dispelled!

"Finally got it!"

Looking at the array diagram in his hand, Chen Shi couldn't help but let out a long sigh of relief.

With this support, he could negotiate with the Chilong and remove the hidden dangers buried in his and Gu Hanying's bodies.

"Walk!"

Without delay, Chen Shi wrapped the battle formation diagram in silk cloth and immediately turned to leave.

After emerging from the cave, I looked around and found no one there.

He breathed a sigh of relief; it seemed he was lucky, as no one had passed by during this time.

The main problem is that it's already dark, and the lush reeds here are over a meter tall, completely covering the cave entrance.

After a moment's hesitation, Chen used pebbles to reseal the cave entrance before quickly leaving.