Writing process of solving practical problems Li Yun is working on a math problem set. On the first day, she did 20% of the total. The ratio of the number of exercises she did on the second day to the first day is 5:4, and there are 32 more problems she didn't do. How many math problems did she do in the first two days!

Writing process of solving practical problems Li Yun is working on a math problem set. On the first day, she did 20% of the total. The ratio of the number of exercises she did on the second day to the first day is 5:4, and there are 32 more problems she didn't do. How many math problems did she do in the first two days!

The ratio of the second day to the first day is 5:4, that is to say, the second day is 1 / 4 more than the first day. That is to say, the proportion of the total number of the second day is 20% + 20% x 1 / 4 = 25%
That is to say, 20% + 25% = 45% of the total in the first two days
That is, 55% of the total number is 32,
45% of the questions are 32x45% / 55% = 26
About 26
(if there are 33 left, you can get the whole number
33X45%/55%=27)

Several calculation problems (writing process)
（1）2X+2-5/1-X （2）X/X-1-X/X+1
（3）1-（a-1/1-a）²÷a²-a+1/a²-2a+1

1, the original formula = 2x-x + 2-5 = x-3
2, the original formula = 1-1-1 + 1 = 0
3, the original formula = 1-1 / a2-a + 1 / a2-2a + 1
=2-3a

After a class finished the experiment of making carbon dioxide, the following experiments were carried out on the recovered mixed solution of hydrochloric acid and calcium chloride (excluding other impurities): take 40 ml of the solution into a beaker and drop 40 g K2CO3 solution with 13.8% mass fraction of solute. The relationship between the mass of K2CO3 solution and the mass of precipitate is shown in the figure (1) The mass of HCl and CaCl2 in 40 ml solution. (2) after the experiment, if the substance in the beaker is evaporated to dryness, the mass of solid is obtained

(1) From the data in the image, it can be seen that there is no precipitation before 10 g, so the potassium carbonate reacting with hydrochloric acid is 10 g. precipitation occurs from 10 to 30, indicating that the potassium carbonate reacting with calcium chloride is 20 g, and the precipitation is 2 g. suppose that the salt acid reacting with potassium carbonate is x, and the potassium chloride is Y & n

There are a few practical problems that can't be solved
There are 100 chickens and ducks in Xiaoming's family. If you sell one twentieth of the chickens, there will be 17 more than ducks. How many chickens and ducks did Xiaoming's family have?
We need formulas, not equations.

There were x chickens and Y ducks
x+y=100
19/20x-y=17
The solution is x = 60, y = 40
So the Ming family used to raise 60 chickens and 40 ducks!
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