Miss Liu took some money to buy exercise books Mr. Liu took some money to the store to buy some exercise books, but it happened to be on sale. This exercise book was sold at a 20% discount. In this way, the money Mr. Liu brought could just buy 50 more exercise books than before. The original price of the exercise book was 2.5 yuan. Please calculate how much money Mr. Liu brought. It's better not to use the solution equation

Miss Liu took some money to buy exercise books Mr. Liu took some money to the store to buy some exercise books, but it happened to be on sale. This exercise book was sold at a 20% discount. In this way, the money Mr. Liu brought could just buy 50 more exercise books than before. The original price of the exercise book was 2.5 yuan. Please calculate how much money Mr. Liu brought. It's better not to use the solution equation

2.5 × 0.8 × 50 (1-0.8) = 500 yuan

At the end of the semester, in order to recognize the excellent, teacher Wang used w yuan to buy prizes. If 2 pens and 3 notebooks were used as a prize, 60 prizes could be bought; if 2 pens and 6 notebooks were used as a prize, 40 prizes could be bought. Suppose the unit price of pen was x yuan / pen, and that of notebook was y yuan / book. (1) please use the algebraic expression of y to express X. (2) if w yuan was used How many laptops can I buy with all my money? (3) If Mr. Wang can buy 30 of the same prizes with this w yuan, he can choose a pen and B notebook as a prize (both prizes must be available). Ask for all possible a and b values

(1) From the meaning of the question: 60 (2x + 3Y) = 40 (2x + 6y), (2 points) simplify: x = 32y. (1 point) (2 points) 60 (2x + 3Y) △ y = 360. (2 points) answer: a total of 360 copies can be sold; (1 point) (3) from the meaning of the question: 60 (2x + 3Y) = 30 (AX + by), substitute x = 32y to get: 32A + B

There are 11 liters of pure alcohol in container a and 15 liters of water in container B. for the first time, pour part of pure alcohol in container a into container B to mix alcohol with water. For the second time, pour part of mixed liquid in container B into container A. in this way, the pure alcohol content in container a is 62.5%, and the alcohol content in container B is 25%. How many liters of mixed liquid are poured into container a from container B for the second time ？

For container B: because the alcohol: mixture = 25%, so the alcohol: water = 25%: (1-25%) = 1:3, that is, the poured alcohol is 15 △ 3 = 5 (L). For container a: the remaining alcohol is 11-5 = 6 (L). After setting, pour x L from container B, then (6 + 25% x) △ 6 + x) = 62.5%, the solution is x = 6. A: pour 6 L of mixture from container B for the second time

If only oxygen and hydrogen are detected in a substance, then the substance
Must be pure or oxide
Or maybe it's a mixture

Mixtures and oxides (pure matter) are possible,
Mixture: water vapor and oxygen; water vapor and ozone; hydrogen peroxide and water
Purities: hydrogen peroxide; water

How to test the material containing carbon, hydrogen and oxygen

After weighing the material, it is burned to produce carbon dioxide and water, proving that it contains C and h, subtracting ch from the total mass, and proving that there is o

How to verify that xylitol contains C element and hydrogen element

Ignite xylitol, cover a dry and cold small beaker on the flame, if there is water mist on the inner wall, it is proved to contain hydrogen. Then cover a small beaker with clear lime water on the inner wall of the flame, if the inner wall becomes turbid, it is proved to contain carbon

Two identical bottles are filled with alcohol solution. The volume ratio of alcohol to water in one bottle is 3:1, and the volume ratio of alcohol to water in the other bottle is 4:1. If two bottles of alcohol solution are mixed, the mass of water in the two bottles is 90g. What is the total mass of the original two bottles of alcohol solution?

Taking the volume of an alcohol bottle as a unit, in one bottle, alcohol accounts for 33 + 1 = 34, 13 + 1 = 14; in another bottle, alcohol accounts for 44 + 1 = 45, water accounts for 14 + 1 = 15; so in the mixture, the volume ratio of alcohol to water is: (34 + 45): (14 + 15), = 3120:920, = 31:9

Two bottles with the same capacity are filled with alcohol solution. The volume ratio of alcohol to water in one bottle is 3:1, and the volume ratio of alcohol to water in the other bottle is 4:1. If two bottles of alcohol solution are mixed, the volume ratio of alcohol to water in the mixed solution is ()
A. 31：9B. 12：1C. 7：2D. 4：1

If the volume of an alcohol bottle is regarded as a unit, then in one bottle, alcohol accounts for 33 + 1 = 34, water 11 + 3 = 14; in another bottle, alcohol accounts for 44 + 1 = 45, water 14 + 1 = 15, so in the mixed solution, the volume ratio of alcohol to water is: (34 + 45): (14 + 15), = 3120:920, = 31

A bottle can hold 1kg alcohol, can it hold 1kg water

To fill one of a, B, C, D in a bottle containing 1 kg water, the volume of a, B, C, d must be equal to or less than the volume of water. The formula volume = mass / density can be used to get the mass. When the mass is fixed, the higher the density is, the smaller the volume is (the larger the denominator is, the smaller the number is)

How many kilos of water can a bottle hold one kilogram of alcohol at most?

Baidu learned that the density of ethanol is 0.8 g / cm3, and the ratio of water is 0.8:1, so it can hold 1 * 1 / 0.8 = 1.25 kg of water