One question, 30 extra points! In no particular order! Extra points for what is clear!

A to C participate in the reaction mass ratio is 2:3

A used to have 20 grams, and the remaining 8g so used 12 grams.

c It turned out that there were 20 grams, and the remaining 2g was 18 grams.

b increased by 30 grams.

So 12:18 2: 3 a c is involved in the reaction.

The ones with less A and C and the more with B are the ones who participate in the reaction.

Mass ratio 12:18:30 = 2:3:5

The reaction can be seen from the title: a + c = b

20 20 20 20 before reaction

8 2 50 after reaction

Reactions 12 18 30

B did not participate in the reaction.

12a+18c=30b

The mass ratio is 12:18

Because this question is very vague, there are only such rough answers. If you guess correctly, this should be a chemistry question in junior high school, and when you are in high school or college, you will find that the question is inaccurate.

a:20-8=12

b:20-50=-30

c:20-2=18

So A and C are reactants, and B is the product.

The mass ratio is: a + c = b

First of all, it is necessary to figure out which two substances react to form which substance, from the title, we can know that the mass of the two substances A and C has decreased, and the mass of B has increased, indicating that the reaction is a and C reaction to produce B, now as long as you can know the mass of the substances participating in the reaction of A, B, and C, it is OK, there is a question to know that the mass of A participating in the reaction is 20-8 12, the mass of C participating in the reaction is 20-2=18, and the mass of B is 30, so the reaction mass ratio is A:C:B=2:3:5

80 minutes.

Water depth: cm.

Rice purchases: 32 (1-1 2) = 64 tonnes.

More rice than flour: 64-32 = 32 tons.

Comprehensive formula: 32 (1-1 2)-32=32 tons.

Find this for yourself.

1) The monthly income of the father is 2,500 yuan, and the monthly income of the mother is 2,000 yuan.

Mom's monthly income is Dad's: 2000 2500 = 80%2) You read 20 pages of a book yesterday and 30 pages today.

More today than yesterday: (30-20) 20=50%3) 6 yuan per kilogram for apples and 8 yuan per kilogram for pears.

Apple** is pear: 6 8 = 75%.

4) You quietly ran 2000 meters yesterday and 2500 meters today.

Today is yesterday's lack of luck: 2500 2000 = 125% 5) You study volatile reform for 3 hours a day and exercise for hours.

Workout time is study time:

There are 5 more girls than boys 1-1 11 = 10 11.

Boys: (152-5) (1+10 11) = 77.

Girls: 152-77=75.

The length of the rope is 7 meters more than the depth of the well and 7 2 = 14 meters less than 2 times the depth of the well.

Well depth: (14+7) (2-1)=21 meters.

Rope length: 21 + 7 = 28 meters.

1 Let the pool volume be x, so the rate of water discharge is x 40 per minute, and the rate of water inlet is x 60 per minute.

There are x 3 divided by x 60 for the time to prevent dirty water and x 2 divided by x 40 - x 60 for the time of water ingress.

So the total time is 80 minutes.

2 Before and after the ice change, the container does not change, so only the height changes, so the volume ratio is equal to the height ratio.

v ice - v water = 1 11 v water So v ice v water = 12 11 i.e. h ice h water = 12 11 The height of the ice after the transformation of the dead ant is centimeters.

So the height of the unburied converted water is centimeters, and the original height is 12 centimeters.

So now the depth of water under the ice is centimeters.

3 Because flour is 32 tons, and half is less than rice, half of the rice is 32 tons.

So the surplus rice is 64 tons, and the rice is 32 tons more than the flour.

5 Let the number of boys be x the number of girls y

So the column binary equation is.

x+y=152 x-x/11=y-5

So x=77 y=75

4 6 I'm sorry, I don't understand what it means, so I won't, I can only help you with this.

1.Solution: There are x number of female students.

4x-8=3x+24

x=24+8

x=3232 4-8=120 (person).

A: There are 120 boys and 32 girls in this school who participate in the math competition.

A: Another 40 meters is just 3 5 of this canal.

A: I read a total of 390 pages in two days.

A: Class 6 (1) donated $200.

2400 (1 4 1 3) = 200 (yuan) Answer: Class 6 (1) donated 200 yuan.

Answer: There are still 1 3 left for the whole journey.

A: 95 trees were planted this year.

The bundle of wires is 72 meters in total.

Set the wires turned out to be a total of x meters.

Column: 3 8 x-15 = 30

Solution: x = 120 meters.

A: The wire used to be 120 meters in total.

A's speed = 180 * 4 = 180 meters per minute.

B's velocity = meters per minute.

A speed: 180 4 = 45 meters.

If the diameter of the largest circle in a square is: 180 4 = 45 meters, then the circumference is: meters.

B's velocity: m.

45 The speed of answering is fast.

The number of people in the whole grade of 5th grade: 105 divided by 25%=420 (person).

Whole school: 420 divided by 40% = 1050 (person).

A: There are 1,050 students in the school.

Suppose there are x people in the fifth grade, and 25% x=105 is x=420

If there is a school with y people, 40% y=420 is y=1050

A: There are 1,050 students in the school.