The fast train is 168m, and the slow train is 184m. If the two trains are running in opposite directions, it takes 4 seconds from meeting to leaving. If they are running in the same direction, it takes 16 seconds from the fast train chasing the slow train to leaving,

The fast train is 168m, and the slow train is 184m. If the two trains are running in opposite directions, it takes 4 seconds from meeting to leaving. If they are running in the same direction, it takes 16 seconds from the fast train chasing the slow train to leaving,

Fast train 55 m / S; slow train 33 m / S
This is a quadratic expression of two variables
(it is strongly recommended to draw pictures. That's very intuitive! If you encounter similar problems in the future, you'd better draw pictures as well.)
Set the speed of fast train and slow train to be x m / s, Y M / s respectively
We get two formulas: 4x + 4Y = 168 + 184
16X=16Y+(168+184)
Finally, x = 55, y = 33
Wonder the origin of the two formulas?
Formula:
When the two cars met (head contact) and left (tail contact), they drove a total of (168 + 184) meters
Formula:
In the process of overtaking, the fast train has to drive (168 + 184) meters more. In the process of overtaking, the slow train is also driving, so the total s of the fast train is s + (168 + 184) meters of the slow train
It should be detailed enough~
God, just a few more words, the sofa is gone! When answering, there is no one in front!
PS: remember: draw! Draw! Draw!
I guess you are from junior high school~
Take 15 coal from pile a and give it to pile B. at this time, the weight of the two piles of coal is equal. How much less is the weight of pile B than that of pile a?
15 × 2 △ 1, = 25 △ 1, = 40%; a: the weight of coal in pile B is 40% less than that in pile a
A and B start at the same time from AB and run in opposite directions. After 7 hours, they meet. A is 20 kilometers slower than B. when they meet, the distance ratio of the two vehicles is 7:9. How many kilometers is the distance between AB and B
Car a is 20 kilometers slower than car B per hour. After 7 hours, car a runs 140 kilometers less than car B,
So car a drove 7 * [140 / (9-7)] = 490 km, and car B drove 9 * [140 / (9-7)] = 630 km,
So the distance between AB and ab is 490 + 630 = 1120 km
20 ÷ (9-7) x (9 + 7) X7 = 1120 km
The distance ratio of the two cars is 7:9 when they meet
Speed ratio 7:9
A speed 20x7 △ 9-7 = 70
B speed 70x9 △ 7 = 90
Distance (70 + 90) X7 = 160x7 = 1120km
Car B is slower than car a by 140 kilometers per hour,
So car a drove 7 * [140 / (9-7)] = 490 km, and car B drove 9 * [140 / (9-7)] = 630 km,
So the distance between AB and ab is 490 + 630 = 1120 km
Suppose the speed of car a is x, then the speed of car B is x + 20
The distance a runs is: 7x
The running distance of B is: 7 (x + 20)
According to the title, the ratio is 7:9
7x:[7(x+20)]=7:9
The solution is x = 70 (km / h)
So the distance between the two places is: [70 + (70 + 20)] * 7 = 1120 (km)
Suppose: the speed of car a is x, then the speed of car B is x + 20
A: 7x B: 7 (x + 20)
When they met, the distance ratio was 7:9,
7x:[7(x+20)]=7:9
The solution is x = 70 (km / h)
So the distance between the two places is: [70 + (70 + 20)] * 7 = 1120 km
An express train is 306 meters long and a slow train is 344 meters long. The two trains run in opposite directions. It takes 13 seconds from meeting to leaving the process. If they run in the same direction, it takes 65 seconds for the express train to catch up with the slow train
The speed of the car is solved by equation
Fast speed x slow speed y
13(x+y)=306+344
65(x-y)=306+344
x+y=50
x-y=10
2x=50+10=60
x=30
A: the speed of the express train is 30 m / s
Solution: let the fast train speed be XM / s and the slow train speed be YM / s
(X+Y)·13=306+344
(X-Y)·65=306+344
X=30,Y=20
Therefore, the speed of fast train is 30m / s and that of slow train is 20m / s
If you are a primary school student, then you can only use the equation of one variable to solve it, then I will use the equation of one variable to solve it!
From the first known condition, we can calculate the sum of the two vehicles' speed per second as: (306 + 344) / 13 = 50m
If the speed of the slow train is x meters per second, then the speed of the fast train is 50-x meters per second
（50-X-X）*65=306+344
Solution: x = 20m is the speed of idle train per second
Fast train speed per second = 50-20 = 30 meters
A: the express... Unfolds
If you are a primary school student, then you can only use the equation of one variable to solve it, then I will use the equation of one variable to solve it!
From the first known condition, we can calculate the sum of the two vehicles' speed per second as: (306 + 344) / 13 = 50m
If the speed of the slow train is x meters per second, then the speed of the fast train is 50-x meters per second
（50-X-X）*65=306+344
Solution: x = 20m is the speed of idle train per second
Fast train speed per second = 50-20 = 30 meters
A: the speed of the express is 30 meters per second. Put it away
Take 15 coal from pile a and give it to pile B. at this time, the weight of the two piles of coal is equal. How much less is the weight of pile B than that of pile a?
15 × 2 △ 1, = 25 △ 1, = 40%; a: the weight of coal in pile B is 40% less than that in pile a
A, B and ab start at the same time and run in opposite directions. They meet in 7 hours. Car a is 20 kilometers slower than car B every hour. The speed ratio of the two cars is 7:9
Why B wants to
20 ÷ (9-7) × 7 = 70
Speed of car a: 20 △ (9-7) × 7 = 70 (km)
Speed of vehicle B: 70 + 20 = 90 (km)
AB distance: (70 + 90) × 7 = 1120 (km)
If the speed of vehicle a is x km / h, then
X / （X+20）=7 / 9
X = 70 km / h
Speed of vehicle B: 70 + 20 = 90 km / h
AB distance: (70 + 90) × 7 = 1120 (km)
Let's put it this way
20×7=140…… What's the difference in seven hours
140÷（9-7）×（7+9）=1120
Car a is 20 kilometers slower than car B per hour, That is to say, the speed of car a is 20 less than that of car B, and the speed ratio of two cars is 7:9, that is to say, the speed of car a is 2 times less than that of car B (7 is definitely 2 times less than that of car 9), two is 20, and one is 10. The speed of car a is 10 times 7 = 70, and the speed of car B is 10 times 9 = 90
Car a is 20 kilometers slower than car B per hour, That is to say, the speed of car a is 20 less than that of car B, and the speed ratio of two cars is 7:9. That is to say, the speed of car a is 2 times less than that of car B (7 is definitely 2 times less than that of car B), two is 20, and one is 10. The speed of car a is 10 times 7 = 70, and the speed of car B is 10 times 9 = 90. According to the speed and the time of meeting, the distance between two places is (70 + 90) × 7 = 1120 (km)
The length of an express train is 168 meters, and that of a local train is 184 meters. If two trains are running in opposite directions, it takes 4 seconds from meeting to leaving. If they are running in the same direction, it takes 16 seconds from the express train chasing the local train to leaving,
Set the idle speed to x meters per second
If you travel in opposite directions, the fast train will take (168 + 184) meters more than the local train
So the speed of express train is (168 + 184) m / 16 S = 22 m / s faster than that of local train
The total distance of two cars is (168 + 184) meters
Then, (168 + 184) m / x + (x + 22 m / s) = 4 s
X = 33 m / S
Then the speed of the express train is 33 m / S + 22 m / S = 55 M
Take 15 coal from pile a and give it to pile B. at this time, the weight of the two piles of coal is equal. How much less is the weight of pile B than that of pile a?
15 × 2 △ 1, = 25 △ 1, = 40%; a: the weight of coal in pile B is 40% less than that in pile a
A and B vehicles meet each other for 9 hours from ab. a vehicle travels 20 kilometers less per hour than B vehicle, and the speed ratio of the two vehicles is 7:9
No equations,
Speed of car B: 20 / (2 / 9) = 90 km / h
Speed of car a: 90 * 7 / 9 = 70 km / h
Distance: (90 + 70) * 9 = 1440 km
Let V A = x, then v b = x + 20
Therefore, X / (x + 20) = 7 / 9, V A = 70 km / h, v b = 90 km / h.
So x = 9 * (70 + 90) = 1440 (km)
20 × 9 = 180 km
180 ÷ (9-7) = 90 km
90 × (7 + 9) = 1440 km
Let a be x km / h and B be y km / h
Car a runs 20 kilometers less per hour than car B
X+20=Y
The speed ratio of the two cars is 7:9
Then x: y = 7:9
From above we can get x = 70, y = 90
A and B two cars respectively from the AB two opposite and 9 hours to meet
So the distance between a and B is s = 70x9 + 90x9 = 1440
An express train is 168 meters long and a local train is 184 meters long. If the two trains are the same, it takes 4 seconds from meeting to leaving. If they are the same, the express train will catch up with the local train and leave
It blooms for 16 seconds,
Speed sum of two cars: (168 + 184) / 4 = 88 (M / s)
Fast train is faster than local train: (168 + 184) / 16 = 22 (M / s)
Express speed: (88 + 22) / 2 = 55 (M / s)
Idle speed: (88-22) / 2 = 33 (M / s)