The first problem is that 20/80=25% (solute mass/solution mass = solute mass fraction);

In the second question, the scores are all 0.9, 8/9, 99% and 0.89, and the scores are 9//kloc-0, 8/9, 99/ 100, 89/ 100, and then 900//kloc-0. 890/ 1000, so the maximum value is 1 125/ 1000, and the minimum value is 890/ 1000. That is, the maximum is 8/9 and the minimum is 0.89;

The third question is to calculate the class size first. Class size = number of boys+number of girls = 12 +20 =30. The first empty boy/girl = 12/20=60.0%, and the second empty girl/class =20/30=66.7%.

The fourth question uses the formula used in the first question. Solute mass =20g, solution mass = solvent mass+solute mass =20g+80g = 100g, so solute/solution =20/ 100=20%.

Question 5: Remaining conductor = original conductor-used conductor = 18m-4.5m = 13.5m Remaining conductor/original conductor = 13.5/ 18=75%.

The quality of soybean oil/raw beans = 1200/3000=40%

The seventh problem is similar to the survival rate/total number of plants =70/80=87.5%.

The passing rate of the eighth question = the number of people who passed/the total number of people, so the number of people who passed = the total number of people * the passing rate =50 people ×96%=48 people.

Question 9: Class attendance/total attendance =47-3/47=93.6%.

The tenth wrong question green area should not be greater than the total area.

Problem 1 1 90%

Question 12 240/(240+60)=80%

Question 13 731/(1-15%) = 860.

Question 14: There are two ways to improve the solution concentration: reducing solvent and adding solute. This question is the second way. Solid transformation means that the second solvent of solute remains unchanged, and the original solvent and solute are calculated first. Solute = 60g× 20% = 12g solvent = 60g- 12g = 48g, sugar water with 40% sugar content, solvent content of 60% and solid solution mass of 48g/60% = 80g, so the sugar content of sugar water with 40% sugar content is 80g-40g.

Question 15 Sector area =(θ/π)*S, where θ is the central angle, S=π*R*R, and r is the radius. Since the central angle is constant, the ratio of solid area is the ratio of S, that is, the ratio of radius square R * r/R * r = (1× 1)/ (.

For question 16, see question 15. The area ratio is θ, which is 1/5, so it is 5 times.

For questions 17, see questions 15 and 16. Nine and a half times

Short answer

The formula of the first question is15 (150/360) × 3.14× 62.8× 62.8cm2 = 5160cm2.

The total number of second questions = (44000+20000+16000) Only = 80000.

Chicken = 44,000/80,000 = 55%

Ducks =20000/80000=25%

Goose = 16000/80000=20%

The third problem, the level limit, can't illustrate books. It's simple.