When Chu Yan was preparing for the exam in Wuxian County, Jiangnan, it happened that there was a huge deficit in the county government's granary inventory. The main bookkeeper checked the accounts for many days without results, and the people were afraid that taxes would be assessed due to the "deficit". Chu Yan, who was desperate, took the initiative to apply for the job on the condition that "if the deficit can be found out, the county government will sponsor scientific research." He used a unique "layered accounting method" to dismantle three years of account books, not only uncovering the officials who had committed theft, but also calculating the flow of misappropriated grain, which relieved the people of the extra burden.
This incident was known to the censor who was passing by, and Chu Yan helped him clarify the loopholes in the calculation of the local "poll tax", and reduced the harsh tax by 30% for the people of a county, and his reputation gradually spread. The imperial censor recommended him to the Ministry of Household Affairs, which coincided with the imperial court's ongoing debate over military pay accounting - the military ration accounts of the ten provinces were in chaos, and the officials of the Ministry of Household Affairs still had no results after counting three months. Chu Yan spent three days sorting out the accounts using the "return to the president's method" and found out the 100,000 taels of silver that had been falsely reported, and was granted an unusual official appointment by the emperor.
After that, he used arithmetic to rectify the salt and iron monopoly, reform the water transportation budget, and formulate a fair tax system. In the midst of the exclusion of the "literary party" and the officialdom game, he always used arithmetic as a blade and served the people as his thoughts. Eventually, he became the Minister of the Ministry of Household Affairs, turning arithmetic from a "minor skill" into an important weapon in the court. While completing the counterattack of a poor family, he also solved the financial dilemma of the Yong Dynasty.
