Zhang Zhu, an astronomer and mathematician in the Tang Dynasty in China, once wrote a math problem on the topic of "Li Bai drinking": "Li Bai is walking in the street, carrying a pot to buy wine. Double it when you meet a store, and drink a barrel when you see flowers (a barrel is an ancient wine set and can also be used as a unit of measurement). I met the flowers in the shop three times and drank all the wine in the pot. How much wine is there? "

Ask for the original amount of alcohol in the pot, and tell the change and final result of the wine in the pot-multiply it by three (multiply it by two) and then subtract it quantitatively (lose weight). To solve this problem, it is generally based on the changed results, using the reciprocal relationship of multiplication and division, addition and subtraction, and gradually reverse reduction. "Drink all the wine in the pot after meeting the flowers in the store for three times" means that there is a bar barrel in the pot after meeting the flowers in the store for three times, a bar barrel after meeting the flowers in the store for three times 1÷2, and then a bar barrel after meeting the flowers in the store for two times 1÷2+ 1.

[(1÷ 2+1) ÷ 2+1] ÷ 2 = 7/8 (barrel)

So, the pot hit 7/8.

The key point of the above solution lies in inverse reduction, which can also be expressed by schematic diagram or line segment diagram.

Of course, if we use algebra to solve this problem, the quantitative relationship will be more clear. There are x barrels of wine in the pot. List the equations according to the meaning of the question.

2[2(2x- 1)- 1]- 1 = 0

X=7/8 (barrel) is obtained by solving.