Please help me solve a math problem, it s about engineering application problems! Urgent! ）

1.First of all, the engineering problem should solve the problem of thought. That is, the problem is known for a while, and you need to look at the total amount of work"Unit 1"That's 1

Then work efficiency x working hours = total workload.

So A's work efficiency is 1 12

B is 15 days to complete 3 4(1 times 75 = 3 4) so B's work efficiency is 1 20

So the cooperation time is 1 divided by 1 12 + 1 20 (I won't forget it, I'll tell you a solution idea).

2.This kind of problem is still easier to do with equations.

Let's say there are x people.

The first time 1 3 got off, that is, there were 1-1 3 people, that is, there were 2 3 x people.

2/3 x+5=75%x

I'm not puzzled either

The most important thing in doing mathematics is the idea of solving the problem, especially the equiquantitative relationship of the equation, and then understanding it. Anything came out.

Good luck with your learning and progress.

If there's anything you don't understand about math and science, you can ask me

1) From the inscription, A completes 1 12 every day, B completes 1 20 every day, 1 12 + 1 20 = 2 15, A and B cooperate to complete 2 15 in one day, so days.

2) When the car is full, there are x people, and after arriving at the station, there are x-(1 3x)+5 people, x=75%.

So x=60 people.

1. Team B completes 75% of this work every day 15 = 5% Team A completes this work every day 1 12

Teams A and B need 1 (1 12+5%) to complete this work 2, solution: set up the original passengers on the car x people.

x×（1-1/3)+5=75%x

1 12 + 1 20 = 2 15, A and B cooperate to complete 2 15 in one day, so days.

When the car is full, there are x people, and after arriving at the station, there are x-(1 3x)+5 people, x=75%.

So x=60 people.

1. To build a road, Team A will complete it in 15 days and Team B will complete it in 12 days. After 4 days of joint training by the two teams, Team B was transferred, and the rest of the route was continued by Team A. How many days did Team A work on it?

Answer: 10 (days).

2. For a project, A will complete it in 20 days alone, and B will complete it in 30 days. A and B did it together for a few days, B asked for leave due to business, and A continued to do it, and it took 16 days from the start of work to the completion of the task. How many days B takes leave.

Answer: 10 (days).

3. A highway should be completed in 12 days by the two road construction teams of A and B. Now the road has been repaired by team A for 3 days, and then repaired by team B for 1 day. If the road is repaired by Team A alone, how many days will it take to complete it.

Answer: 120 (days).

4. The master and apprentice jointly processed a batch of parts, and the total number of parts was processed in 2 days. If all the parts are processed by the master alone, it will take 10 days to complete. If it is all processed by apprentices, how many days will it take to complete.

Answer: 15 (days).

5. A project will be completed in 30 days by the cooperation of teams A and B. If Team A works alone for 24 days and Team B joins the cooperation, after 12 days of cooperation between the two teams, Team A leaves due to an incident, and Team B continues to do it for 15 days before it is completed. How many days would it take for this project to be completed by Team A alone.

Analysis: A does it for 24 days first, and B does it for 15 days at the end, which can be understood as 15 days of joint work and 12 days of joint work, for a total of 27 days. =90 (days).

6. For a project, teams A and B can complete the whole project every day. Team A can complete the whole project after 3 days and Team B for 5 days. If the whole project is done by Team B alone, how many days can it be completed.

It can be understood that the two teams did it together for 3 days. 10 (days).

7. A project can be completed in 10 days by team A alone, and team B can be completed in 30 days. Now team A has a 2-day break and team B has a 8-day break during the cooperation period between the two teams (the two teams do not rest on the same day).How many days it took from start to finish.

Analysis: It can be understood as doing a lot of 6 days. 11 (days).

8. A project, if team A does it alone, can be completed in 6 days. A has 3 days of work, B has 4 days to complete. After the two teams work together for 2 days, Team B will do it alone, and Team B will have to do it for how many days to complete.

Answer: The ergonomics of A are 1 6, and the ergonomics of B are 1 6*3 4=1 8. 3 (days).

9. A project can be completed by A alone for 63 days, and then by B alone for 28 days; If A and B work together, it will take 48 days to complete. Now A does it alone for 42 days, and then B does it alone, so how many more days does B need to do it?

A alone takes 84 days to complete, and B alone takes 112 days to complete; B will take another 56 days.

10. A job A does for 6 hours first, and B then does it for 12 hours to complete. A does it for 8 hours, B then does it for 6 hours, but if A does it for 3 hours and B does it, how many hours will it take?

A can be completed in 10 hours alone, and B alone can be completed in 30 hours; B will take another 21 hours.

4 (hours) A: It will take 4 hours to complete the correction.

500x+200(300-x)=900

x = 100 minutes.

The total return is 10,000.

2. Set the water consumption to be x cubic meters.

If x does not exceed 15 cubic meters.

The fee is (<42 yuan.

then x>15

x = 20: The household consumes 20 cubic meters of water in a month.

500x+200*(300-x)=90000x=100A100 B200 Benefits: 100*9000+200*2000=1.3 million.

Wanhualai) The title feels a little wrong, if the water consumption is 7 cubic meters, the excess part cannot be counted!!

Believe me, it makes more sense to read * signifies multiplication.

Your first question is less conditional, is it how to send advertisements on an average basis or in the most profitable way?

Your second question is how much does it cost to charge between 5 and 15 cubic meters?

Set up in Company A advertising A minute. Advertise B minutes in Company B.

a+b<=300

The company's earnings y = (3000-500) a + (2000-200) b - 90000

2500a+1800b-90000

700a+1800×300-90000

700a+450000

It means that the company's advertising benefit in Company A is 700 300 + 450,000 660,000 yuan.