After reading two books in a row, Zhu Di finally discovered the clue.

When looking at each ledger, Guo An was muttering a few words every time he turned the page.

"Are you learning from Master Daoyan to chant sutras?"

“……”

Guo An was interrupted, and looked up at Zhu Di in a daze, "Your Highness, are you talking about the lower official?" ”

"Could it be that the king is talking to himself?" Zhu Di said with a disgusted face.

Guo An pursed his lips and said with some disdain: "Your Highness is so ignorant, the lower official is calculating!" ”

Zhu Di's face suddenly darkened, "You thief, dare to look down on this king?" ”

Guo An was taken aback, secretly slapped himself in his heart, and hurriedly smiled: "Your Highness heard it wrong, Xiaguan said that this is Xiaguan's original oral arithmetic method, only Xiaguan can do it, and His Highness naturally hasn't seen it!" ”

Zhu Di's face was full of curiosity, "Oral arithmetic? ”

"You go on!"

"Yes, Your Highness!"

Guo An hurriedly continued to check the ledger, and now there are dozens of old men lined up behind him, he must hurry!

On the side, looking at Guo An, who was muttering in a low voice again, Zhu Di listened carefully for a long time, but still didn't hear a word clearly, and couldn't help but be a little anxious.

If you learn this miraculous oral arithmetic, whether it is counting the baggage materials in the army or arranging the troops, it will have a huge effect.

Therefore, after Guo An continued to check the three ledgers, he finally couldn't help it.

"You're so slow to check alone, why don't you call a few scribes to check!"

“……”

Guo An's train of thought was interrupted again, and he couldn't help frowning slightly, "Your Highness, don't make trouble, there are still so many old people waiting outside, and the lower officials have to hurry up and get through it again."

These scribes are slow to count one by one, and the lower officials can beat them alone, so it is better to let them write IOUs, which is to make the best use of people! ”

Zhu Di said: "It's okay, you have a louder voice, this king listens to your oral calculation process!" Perhaps, when this king was a child in the main hall, he also learned this kind of oral arithmetic! ”

"Be louder...... Forehead! ”

Guo An subconsciously glanced at Zhu Di, but found that Zhu Di was looking at him with confidence.

"Good!"

Guo An chuckled, he could be regarded as having seen how thick-skinned this famous Yongle Emperor in history was!

"Forty stones, thirty stones, seventy stones, fifteen stones, eighty-five stones, twelve stones, ninety-seven stones...... Nine stones, one thousand one hundred and eighteen stones! ”

Before the time of a cup of tea, Guo An seemed to have just recited the number.

Then, he wrote down the numbers he had calculated on the ledger in his hand and handed them to the old man who was waiting on the side.

"Take it and get the IOU!"

"Thank you, county!"

When the old man left, Guo An continued to take the account book and read it.

At the same time, speak out.

But in Zhu Di's eyes, Guo An in front of him was still thinking about the number!

When the old man in the public house changed, Zhu Di still didn't understand, and his face couldn't help but get darker and darker.

Fortunately, a scribe on the side brought a chair very discerningly, which did not make His Royal Highness King Yan tired.

"I don't know if the oral arithmetic of the lower official is the same as what His Royal Highness learned in the main hall of the Imperial Palace?"

After the old people in the public house went out, Guo An asked Zhu Di with a smile.

"It's different!"

Zhu Di replied lightly, "The oral calculation you use is the same as Master Daoyan's recitation of scriptures, and I have never appeared in the Ming Dynasty!" ”

"Then I wonder if Your Highness is interested in this method of oral arithmetic?"

Guo An continued to ask: "With this method, any mistake in the account book will not escape the eyes of His Highness!" ”

"Huh?"

Zhu Di was overjoyed, "This is your unique technique, are you willing to teach this technique to this king?" ”

Guo An hurriedly said: "In the past few months, His Royal Highness has helped Xiaguan Wanping County a lot, Xiaguan is not the kind of ungrateful person, His Royal Highness wants to learn, Xiaguan can't ask for it!" ”

"Huh?"

Zhu Di's face sank, "Isn't it your mother's who wants to teach this king?" Why did you become a king who wanted to learn? ”

What a shame!

Guo An's face stiffened, "Yes, yes, it is the lower official who wants to repay His Highness's kindness and wants to teach His Highness!" ”

Hearing this, Zhu Di nodded with satisfaction.

"In this way, why don't you quickly teach this king, the kind of magical arithmetic method you use?"

"Your Highness, wait a moment!"

As he spoke, he walked to the side.

Ning Deyou and the servants of the household were also full of joy, and they all hurriedly followed up, and under Zhu Di's surprised gaze, they lifted out two wooden shelves of the same size from the corner of the public house.

On each wooden shelf, there is a wooden board the size of a table, which has been painted with black paint, and it is pitch black.

And on a wooden board, there is a large string of Yiren numbers written.

Seeing this, Zhu Di suddenly realized.

"Are you counting in Arabic numerals?"

"Your Highness is wise!"

Guo An nodded slightly, and after straightening the blackboard, he took out a few limestones that had been cut and the size of a human finger from a wooden box on the side.

"Your Highness, although the strength of those overseas Yi people is not as good as mine, the number they invented is a good thing. Not only is it easy to write, but it's also easy to calculate! ”

"When these numbers are added together, the rest of them can be superimposed and written, one plus two, or twelve plus twenty, or one hundred and ten......."

"It's just the addition and subtraction of numbers, if you add a ninety-nine multiplication formula, then the multiplication of any number of numbers can be calculated, such as ......

And the division is the same......"

Guo An said it very quickly and clearly, but Zhu Di, who came into contact with Arabic numeral calculation for the first time, was stunned.

"How is it, I wonder if Your Highness can understand?"

After finishing the last one, Guo An put down the lime pen in his hand, patted it gently, and asked Zhu Di.

Zhu Di said with disdain: "It's just a few numbers brought into my Ming Dynasty, how can this king not understand?" ”

Guo An laughed directly, "Your Highness is really smart! Now that His Highness has learned, then the lower officials will have lunch, I wonder if His Highness is also with him? ”

"Lunch, when is it?" Zhu Di asked.

Guo An hurriedly replied: "Your Highness, it's time now, aren't you hungry?" ”

"Not in time?"

Zhu Di was startled, looked up and looked out the door, and the old men outside had already left cleanly!

"The old men are gone, too?"

Guo An said, "Your Highness, after they have lunch in the afternoon, they will continue to come to the Yamen!" ”

After Zhu Di groaned slightly, he said: "In this way, since you are kindly invited, this king will taste the food of your county government!" ”

“……”

Guo An sighed softly, "The lower officials are grateful!" ”

"Hahaha, you're a sincere person!"

“……”

……