1. A passenger car and a freight car leave from a and B at the same time. After six hours of meeting, the two cars advance at the same speed, and the passenger car arrives in four hours At this time, how many hours does the truck have to travel to station a? 2. A factory produces a batch of pesticides, which takes 12 days for a and 15 days for B. the two vehicles jointly produce for 7 days, exceeding 42 tons. How many tons of pesticides are planned to be produced? 3. A batch of cement is planned to be produced in 15 days by workshop a alone. If it is produced jointly with workshop B, it will only take 8 days to complete. Now after several days of production by workshop a alone, the remaining tasks will be completed indirectly by workshop B. in this way, it takes 17 days. How many days has workshop B produced? (equation) If you are satisfied, 50 points will be added. Thank you. I am in urgent need! There is a batch of materials to be copied. It takes 11 hours for machine a to copy separately, and 13 hours for machine B to copy separately. When two copiers A and B copy at the same time, due to mutual interference, they print 28 pieces less per hour. Now it takes six hours and 15 minutes for the two copiers to finish printing at the same time. How many copies are there?

1. A passenger car and a freight car leave from a and B at the same time. After six hours of meeting, the two cars advance at the same speed. The passenger car arrives at the station after another four hours. How many hours does the freight car have to travel to reach the station a?
The speed ratio of freight car to passenger car is 1 ／ 6 = 1 ／ 4 = 2:3
The freight cars that run for 6 hours should run for 6 △ 2 × 3 = 9 (hours)
The truck has been running for 4 hours, and it still needs to run for 9-4 = 5 (hours)
2. Plan to produce X tons
(x+42)/(x/12+x/15)=7
X = 840 tons
3. Workshop a produces x, workshop B produces y. workshop B produces t days
15x=8(x+y)
(17-t)x+ty=15x
The solution is t = 16
Set a to print x sheets an hour and B to print y sheets an hour
（x+y)25/4-25*28/2=11x
11x=13y
The solution is y = 275
So this batch of data is 275 * 13 = 3575
Thank you

Given the set a = "A2, a + 2, - 5", B = "10, 3a-5, A2 + 3", and a ∩ B = "- 5", find the real number a

If a ∩ B = {- 5}, then:
1. If 3a-5 = - 5 and a = 0, then a = {0,2, - 5}, B = {10, - 5,3}
2. If a & # 178; + 3 = - 5, it is impossible
So a = 0

If the number of a increases by 1 / 3 and the number of B increases by 2 / 5, then the two numbers are equal. What is the original number of a?

If the number of a increases by 1 / 3 and the number of B increases by 2 / 5, then the two numbers are equal. What is the original number of a?
4 / 3 of a = 7 / 5 of B
Number a to number b = 3 / 4 to 5 / 7 = 21 to 20
21:20 = 21 / 20 = 21 / 20

How many continuous numbers are there in the 100 natural numbers of 0 99

The natural number n does not produce carry when adding n + (n + 1) + (n + 2) vertically, then n is called "continuous number", that is, the number of bits of natural number n does not exceed 2, and other digits do not exceed 3. Therefore, there are 1c3 * 1C4 = 12 0,1210,111220,212230,31,32 in 0 ~ 99... 9 (n 9)

Car a and car B go from city a to city B at the same speed. Car a goes 12 kilometers first before car B starts. Car a returns to city B immediately and meets car B at 14 places (from city B to city a). How many kilometers are there between city a and city B?

A: the distance between the two cities is 24 km

If the triangle ratio is 1:2:3, what is the degree of the triangle's internal angle?

Respectively
180 × 1 ÷ (1 + 2 + 3) = 30 degrees
180 × 2 ÷ (1 + 2 + 3) = 60 degrees
180 × 3 ÷ (1 + 2 + 3) = 90 degrees

No.3: every six minutes. No.5: every eight minutes. The starting stations of No.3 and No.5 are all here. They started at the same time
After the two buses start at the same time, how many minutes will it take for the two buses to start at the same time for the second time?
It's a process!

6=2*3
8=2*2*2
6 * 8 / 2 = 24 minutes
By hand, the Watcher will take me
Don't copy from others
Finally, I wish you happy every day

When the equation 3a-b = 2a-b is deformed
When the equation 3a-b = 2a-b is deformed
Because 3a-b = 2a-b,
So 3A = 2A (the first step),
So 3 = 2 (step 2)
Please answer the questions
What's the basis for the first step----------
The second step is to draw a wrong conclusion, which is caused by-----------

The first step is to add the same number to both sides of the equal sign, and the equation still holds
The reason for the error in the second step is that if both sides of the equal sign are divided by the same number that is not zero, the equation still holds
In this problem, both sides are divided by the unknown x, and X is exactly 0

(1) find out the sum of the speeds of the two trains and the time it takes for the slow train to pass a window of the fast train when the two trains are running in the same direction. (2) if the two trains are running in the same direction, the slow train's speed is lower
The two trains run on two parallel tracks, of which the length of the express train is 100 meters and the length of the local train is 150 meters. When the two trains run towards each other, it takes 5 seconds for the express train to pass a window of the local train (from the point where the front of the express train reaches the window to the point where the rear of the train leaves)
(1) how long does it take for the slow train to pass a window of the fast train when the two trains are running opposite each other?
(2) if two trains are traveling in the same direction, the speed of the slow train is 8 m / s, and the fast train chases the slow train from the rear, then how many seconds does it take for the fast train to catch up with the slow train from the front to the rear and leave the slow train from the rear?

(1) Let v be the sum of the two vehicle speeds,
Then 5V = 100
We get v = 20 m / s
When the two trains are facing each other, the time taken for the slow train to pass a window of the fast train is t = 150 / 20 = 7.5 seconds
(2) Slow speed V1 = 8 m / s, then fast speed V2 = 20-8 = 12 m / s,
Then 100 + 150 = (v2-v1) t
The solution is t = 62.5 seconds

The asymptote equation of hyperbolic 9 / x square - 4 / y square = 1 is

The asymptote equation of hyperbola x * x / A * a-y * y / b * b = 1 is y = + - B / A, so
The asymptote equation of hyperbola with 9 / x square - 4 / y square = 1 is y = 2 / 3 or y = - 2 / 3