Both trains run from city a to city B. It takes three hours for car a and two hours for car B. It is known that the speed of car B is less than twice that of car a 40 km. What's the speed of a and B? What's the distance between AB and Beijing?

Let v a be XKM / h, then v b be (2x-40) km / h. according to the title, we get 3x = 2 * (2x-40), and the solution is x = 80km / h. therefore, the speed of car a is 80km / h, and that of car B is 120km / h, and the distance between the two places is 240km

When doing a division, consider the divisor as 40. The original divisor is between () and ()

The original divisor is between 35 and 44
It's not difficult. I'll give you a few examples to show you. Usually, this kind of question is about the size and scope of quotient
120 ／ 38 () 4 is larger than the size, then 38 is regarded as 40, then 120 ／ 40 is naturally less than 4
In other words, the original divisor is regarded as an approximate number according to the characteristics of the divisor. In general, it is the number of the whole ten, and sometimes it is the number ending with 5
In other words, your problem is to take the original divisor as 40 and find out what the original divisor is, then the approximate number of 40 is only between 35 and 44
If you don't understand, ask me!

The plane flew 180 kilometers in 10 minutes. What's its speed, kilometers per hour, and meters per second

10 minutes = 1 / 6 hours = 600 seconds
180 km = 180000 M
180 △ 1 / 6 = 1080 (km / h)
180000 △ 600 = 300 (M / s)
A: its speed is 1080 kilometers per hour and 300 meters per second

Given that positive numbers x and y satisfy 2x − y ≤ x − 3Y + 5 ≥ 0, then the minimum value of Z = (14) x · (12) y is 0______ ．

When the feasible region ∵ z = 4-x · (12) y is transformed into a Z = 2-2x-y straight line Z1 = - 2x-y passing through point a (1, 2), the minimum value of Z1 is - 4, and the minimum value of ∵ z = 2-2x-y is 2-4 = 116, so the answer is 116

If the car travels 15 kilometers more per hour from tunnel a to tunnel B than before, it will take 5 / 6 of the original time. If the car travels 15 kilometers less per hour, it will not take much time

So the time is 5 / 4 of the original
Let the distance be y and the velocity be X
y/x=1,y/(x+15)=5/6,
y/(X-15)=5/4

3x-3 / 2 + 1 = 5x essential process

3X-3/2+1=5X
3X-1.5+1=5X
3X-0.5=5X
3X-0.5-5X=0
3X-5X=0.5
-2X=0.5
X=-0.5/2
X=-0.25

For a batch of goods, 2 / 5 of them were transported in the first time, and the remaining 1 / 5 were transported in the second time. What percentage of the goods were transported in the two times?

(1-2 / 5) × 1 / 5 = 3 / 25 total: 2 / 5 + 3 / 25 = 13 / 25

It is known that y-m and 3x + n are proportional functions (m.n is a constant). When x = 2, u = 4, x = 3, y = 7, the analytic expressions of Y and X are obtained
How to bring in x = 2Y = 4 and x = 3Y = 7? Be more detailed

According to y-m and 3x + n positive proportion function (y-m) / 3x + n) = constant a
The change is y = 3ax + an + M
A (an + m) is two constants
That is y = BX + C
Substituting x = 2Y = 4 and x = 3Y = 7
B = 3, C = - 2
The analytic formula of Y and X is y = 3x-2
I haven't done a problem for more than ten years. I majored in liberal arts. Recently, my head is a little stiff, so I come to practice my brain. Don't blame me if I'm wrong

There are 60 male workers in a workshop, one fourth more female workers than male workers. How many female workers are there?

Answer 60 * (1 + 1 / 4) = 75

1. If the first-order function y = (- K + X-5) / 3 and y = (14k-3x + 4) / 2 intersect in the fourth quadrant, then the value range of K?
2. The relationship between the drug content in blood per milliliter and the time t after taking a certain drug
If T < 2, y = 3T
If t > 2, y = (- 3 / 4T) + (15 / 2)
According to the regulations, when the drug content in every milliliter of blood is not less than 4 micrograms, the treatment is effective
If someone takes medicine for the first time in a day at 8:00 a.m., ask how to arrange the time and frequency of taking medicine in 24 hours

The point of intersection (x, y) is the common point of the graph of two first-order functions. There are two simultaneous analytic solutions to the equations of X, y. The results are as follows
X = 4K + 2, y = k-1, because the intersection point is in the fourth quadrant, the abscissa x = 4K + 2 > 0, and the ordinate y = k-1 = 4 get: T14 / 3 but t = (14 / 3 + 2) but t = 4, the solution is: T = 4
T: t

Both trains run from city a to city B. It takes three hours for car a and two hours for car B. It is known that the speed of car B is less than twice that of car a 40 km. What's the speed of a and B? What's the distance between AB and Beijing?