Solving ten problems of solving inequality, with solutions

Solving ten problems of solving inequality, with solutions

1、3x+70>100 3x >100-70 3x>3O x>10
2、2x2
5、5X-2≥3（X+1）5X-2≥3X+3 2X≥5 X≥5/2
6、1/2X+1＞3/2X-3 1/2X-3/2X＞-3-1 -X＞-4 X＜4
7、1/2（X+8）-2＞0 1/2X+4-2＞0 1/2X＞-2 X＞-4
8、2（X-3）≤4 X-3≤2 X≤5
9、5X+6＜3X 2X＜-6 X＜-3
10、2（1+X）＞3（X-7） 2+2X＞3X-21 -X＞-23 X＜23
(because you didn't say how many yuan and how many times, so what I give you is the inequality equation of one yuan and one time, do you think it's ok?)

Solve the inequality system under the seventh grade 10 application problems! To solve the formula and results!
The answer must not be accurate
1. A worker plans to process 408 parts in 15 days, 24 parts per day in the first three days. How many parts must be processed at least every day in order to exceed the specified time?
2. A factory produces a kind of mechanical parts, the fixed cost is 20000 yuan, the cost of each part is 3 yuan, the selling price is 5 yuan, the tax should be paid is 10% of the total sales, in order to make the net profit exceed the fixed cost, how many parts should be produced and sold at least?
3. A 40 kg insecticide powder with a drug content of 15%. Now 50 kg of the same insecticide powder with higher drug content is mixed with it, so that the drug content after mixing is between 25% and 30% (excluding 25% and 30%). The range of drug content of the powder used is calculated
4. Wang Yikai's home is 2.1km away from the school, and now he needs to walk in 18 minutes. It is known that Wang Kai's walking speed is 90m / min, and his running speed is 210m / min. how many minutes does Wang Kai need to run at least?
5. A person has several red and white balls. It is known that the number of white balls is less than that of red balls, but the number of white balls is two times more than that of red balls. If you write the number "2" to each white ball and the number "3" to each red ball (only one number can be written on each small ball), the total number of numbers on all small balls is 60, then how many white balls are there? How many red balls are there?
6. Give two baskets of apples to class A and class B. one person in class a gets six apples, the others get 13 apples, one person in class B gets five apples, and the others get 10 apples. If the number of two baskets of apples is the same, and more than 100 apples and less than 200 apples, how many apples are there in class A and class B?
7. An engineering team needs to recruit 150 workers of type A and type B. the monthly salary of workers of type A and type B is 600 yuan and 1000 yuan respectively. Now the number of workers of type B is required to be no less than twice of that of type A. when we ask how many workers of type a and type B are recruited, can we make the monthly salary minimum?
8. According to the following ancient poem,
I asked Li Sangong, who opened the shop,
From customers to the shop
There are more than seven guests in one room,
One room with nine guests and one room empty,
How many guests and rooms are there
9. A school rewards students. One of the first grade winners gets 3 prizes, and the others get 7 prizes; one of the second grade winners gets 4 prizes, and the others get 9 prizes. If the number of winners in two grades is different, but the number of prizes is equal, and the number of prizes in each grade is more than 50 but not more than 100, how many winners are there in two grades?
10. There are two inlet pipes in the reservoir of a water plant. The inlet speed of each inlet pipe is 80 t / h, and the total outlet speed of all outlet pipes is 120 t / h. It is known that 400 t of water has been stored in the reservoir
(1) When two inlet pipes enter water and all outlet pipes discharge water at the same time, write the algebraic expression of time t (hour) for the existing water quantity y (ton) in the reservoir
(2) According to the design requirements of the water plant, when the storage capacity of the water storage pool is less than 80 tons, the water discharge must be stopped. Under the condition that the raw water quantity changes, one inlet pipe is used to enter the water and all outlet pipes are used to discharge the water at the same time. How many hours can the water be discharged at most?
11. There are red, blue and white balls in one person's pocket. The number of blue balls is at least half of the number of white balls, but at most the number of red balls. If the total number of white balls and blue balls is at least 55, how many red balls are there at least?

1： Solution: in the first three days, 24 pieces are processed every day. In three days, a total of 72 pieces are processed.. 408-72 = 336 pieces, 15-3 = 12 pieces, so 336 / 12 = 28 pieces, so at least 28 pieces are needed every day, so as to exceed the limit
2： Solution: we need to use the equation to solve this problem. Let X be the number of parts sold and 5x be the sales volume. If the tax is deducted by 10%, then 90% will be left. 5x times 90% = 4.5X, 4.5x-3x (cost) = 1.5x (net profit). Because the net profit is more than 20000, so 15x ≥ 20000 is about 13334
3： Solution: the known drug is 40 kg in total, and the drug content is 15%. Then the real drug content is 6 kg. After adding 50 kg of drug, the total drug content is 90 kg, and it is required to be 25% ~ 30% after mixing. Then 90 times 25% ~ 30% = 22.5 ~ 27 kg of total drug content. Because the original drug content is 6 kg, the drug content is 16.5 ~ 21, and the drug content range is 16.5 ~ 21 / 50 = 33% ~ 42%
4： Solution: let's put it this way. If Wang Kai runs all the way, he can run 3780 meters in 18 minutes, which is far more than 2100 meters. If one minute's running turns into walking, he will walk 120 meters less in one minute, and then he will run 1680 meters more than 2100 meters in the whole process. If he reduces the 1680 meters, he can turn 14 minutes' running into walking, that is, a total of 840 meters in four minutes, 14 minutes walk, a total of 1260 meters, a total of 2100 meters
5： Solution: still use the method of the fourth question, if all are red balls, then 20 (because 20 * 3 = 60), the number sum of two red balls is 6, the number sum of three white balls is 6, so 2 red balls = 3 white balls, then start to replace, the first is 18 red balls, 3 white balls, not conforming, 16 red balls, 6 white balls, not conforming, 14 red balls, 9 white balls, conforming, 12 red balls, 12 white balls, not conforming, so there are 14 red balls and 9 white balls
6： Solution: if there are 13 apples in class A and 10 apples in class B, then there are 13A + 6 apples in class A and 10B + 5 apples in class B. the solution is a = 13 and B = 17, so there are 14 apples in class A and 18 apples in class B
7： Solution: this problem seems to be a bit strange. Since the salary is low, the less type B is, the better. But it can't be less than twice that of type A, so it's just twice that. So 50 for type A and 100 for type B
8： Solution: suppose there are y guests, X rooms, 7x + 7 = y, y ≥ 9 (x-1) ≥ Y-9, the solution is x = 8
9： Solution: let's assume that the person who gets 7 rewards in grade one is x, and the person who gets 9 rewards in grade two is y, 7x + 3 = 9y + 4. The solution is x = 4 and y = 3, so there are 5 in grade one and 4 in grade two
10： Solution: (1) the total water inflow of two water pipes is 160 t / h, and the water outflow is 120 t / h, so the net water inflow is 40 t / h, so y = 400 + 40 t
(2) The total water inflow of a water pipe is 80 t / h, and the water outflow is 120 t / h, so the net water outflow per hour is 40 / h, 400-80 = 320 (the maximum amount of water that can be discharged), 320 / 40 = 8, and the maximum amount of water discharged is 8 hours
11： I can't give you a specific method for the last question. Let me give you an answer. There are at least 19 red balls, which should be right

The reward for 24 inequality application questions is 10 points. I only have this point. How many can I give
Can give a few calculate a few, it is to want "solution. Of" applied problem
No need to answer. I'm a student in grade one

First:
A school run factory has produced a batch of new products. There are two kinds of sales schemes. Scheme 1: sell the batch of products at the beginning of this semester and make a profit of 30000 yuan, then reinvest the investment of the batch of products and the profit of 30000 yuan, and make a profit of 4.8% at the end of this semester. Scheme 2: sell the batch of products at the end of this semester and make a profit of 35940 yuan, However, 0.2% of the invested capital should be paid for safekeeping
(1) When the investment of this batch of products is how much yuan, the profit of scheme 1 and scheme 2 is the same?
(2) According to the amount of investment required, discuss which of the two schemes is more profitable
answer:
Suppose the investment of this batch of products is x yuan
The profit of scheme 1 is 30000 + (x + 30000) * 4.8% = 0.048x + 31440
The profit of scheme 2 is 35940-0.2% x = 35940-0.002x
(1) When the investment of this batch of products is how much yuan, the profit of scheme 1 and scheme 2 is the same?
order
0·048x+31440=35940-0·002x
x=90000
When the investment of this batch of products is 90000 yuan, the profits of scheme 1 and scheme 2 are the same
(2) According to the amount of investment required, discuss which of the two schemes is more profitable
order
0·048x+31440＞35940-0·002x
x＞90000
When the investment is more than 90000 yuan, the scheme will benefit
order
0·048x+31440＜35940-0·002x
x＜90000
When the investment is less than 90000 yuan, scheme 2 will benefit
Second:
In a test, there are 20 questions, 5 points for one question, 2 points for one wrong question, and no points for no answer. Xiaoming has two questions not answered, at least how many questions are answered correctly, and the total score is not less than 60 points?
answer:
Let's answer question x correctly
According to the meaning of the title:
5X-2(20-2-X)>60
7X-36>60
7X>96
X>96/7
Take the excess value x greater than or equal to 14
Third:
For autumn outing, if you rent several 48 seat buses, it will be full; if you rent 64 seat buses, you can rent one less, and one bus is not full, but more than half. It is known that it costs 250 yuan to rent 48 seat buses and 300 yuan to rent 64 seat buses. Which bus is more cost-effective?
Answer: there are x passengers
According to the meaning of the title:
64[(X/48)-1]>X
64[(X/48)-2]

A and B ride from a to B at 8:00 in the morning. A is 6 kilometers faster than B every hour. After arriving at B at 12 hours at noon, a immediately returns to a and meets B 15 kilometers away from B. how far is the distance between a and B?

At the same time, a traveled 30 kilometers more than B
30 △ 6 = 5 (hours) every hour is 6 kilometers more than B. 5 hours is 30 kilometers more than B. it means that both of them drove for 5 hours when they met. It takes 4 hours from 8 o'clock to 12 o'clock, which means that the speed of a is 15 km / h, so the distance of AB is
(12-8) X5 = 20 km
Don't understand, ask me!

A practical problem in the second grade of junior high school@@@@@@@@@@
At the beginning of 2008, a snow disaster occurred in the south of China. The wire cup of a certain place was broken by snow. The maintenance team of the power supply bureau had to go to the suburb 30 kilometers away for emergency repair. The maintenance workers rode motorcycles first, and 15 minutes later, they loaded the required materials and set out. As a result, the two vehicles arrived at the emergency repair point at the same time. It is known that the speed of the emergency repair vehicle is 20 kilometers faster than that of the motorcycle per hour

Motorcycle speed = 40 km / h
Maintenance vehicle speed = 60 km / h
Set the arrival time as t
The speed of motorcycle is V, and the speed of rush repair vehicle is V + 20
V×（t+0.25）= 30
（V+20）×t =30
By solving the equations, v = 40, t = 0.5
That is to say, the speed of motorcycle is 40 km / h and that of emergency repair vehicle is 60 km / h

Insurance calculation problems,
Zhang and his father took their daughter to travel in a car. Unfortunately, they were all killed in a car accident. Zhang's wife died of grief after hearing the news. Zhang insured his father, his daughter and himself for 60000 yuan, 40000 yuan and 60000 yuan respectively, The other two insurance policies did not specify the beneficiary, but Zhang's female insurance policy did not specify the distribution of insurance money. Zhang's mother and father-in-law had a dispute over the total amount of 160000 yuan insurance money after the funeral. How should the case be paid, the specific reasons and the calculation process

This topic seems very troublesome. In fact, it is very simple as long as we analyze it
There are three insurants and two beneficiaries. The three insurants are Zhang, his father, and Zhang's daughter. The insured amount is 64000. The two beneficiaries are Zhang's wife and Zhang's mother. Zhang's father-in-law is not among the beneficiaries, but he can still get part of the money
I