A math problem of average difficulty, a difficult math problem?

Let A and B each need x and y days, then there is.

1/x+1/y=1/24

20/x+40/y=1

Solve this equation to get x 30 days, y 120 days.

If A and B each need x and y yuan per day, there will be.

24(x+y)=120

20x+40y=110

To solve this equation, we get x million yuan, y million yuan.

Therefore, it takes 30 days for A to complete it alone, 1.35 million yuan; It takes 120 days and 600,000 yuan to complete it alone.

Let A be completed alone for a total of A days, and B alone for a total of B days.

1/(1/a+1/b)=24

1-20/a)*b=40

a=30b=120

Set A must be $00,000 per unit of work time, and B must be $10,000 per unit of time per work.

24(x+y)=120

20x+40y=110

x = So teams A and B complete the project on their own, and it takes 30,120 days each.

Teams A and B completed the project on their own, each requiring $135,600,000 each.

There are two engineering teams, A and B, to repair one project. If A and B teams work together, it can be completed in 24 days, and it takes 1.2 million yuan, and if A does it alone for 20 days, the rest of the project is done by B, and it takes 40 days to complete, so it takes 1.1 million yuan

1) How many days does it take for teams A and B to complete the project alone?

First take out 20 days out of the 40 days that B does, and A and B work together to complete the project in 20 days.

There is still a total project left.

This is b20 days dry, every day to do the total project.

b. Completed the total project.

1 1 120 = 120 (days).

A is required to finish the total project.

1 (1 24-1 120) = 30 (days).

2) How many yuan does it cost for teams A and B to complete the project alone?

Let A need x million yuan to complete alone, and B needs y million yuan to complete alone, according to the topic.

x*24/30+y*24/120=120

x*20/30+y*40/120=110

The solution. x=135

y=60

n lines should have a maximum of several intersection points, and the method is c n=n(n-1) 2

Think of it this way inductively.

2 straight lines have 1 intersection.

3 straight lines have 3=2 3 2 intersections.

4 straight lines have 6=3 4 2 intersections.

5 straight lines have 10 = 4 5 2 intersections.

6 straight lines have 15 = 5 6 2 intersections.

That n straight lines