A and B are going from AB to B at the same time. They meet in 12 hours. After meeting, a goes to B in 8 hours and asks B to reach a in a few hours

A and B are going from AB to B at the same time. They meet in 12 hours. After meeting, a goes to B in 8 hours and asks B to reach a in a few hours

A meet before 12 hours, meet after 8 hours, so a complete line to 20 hours
So a goes 1 / 20 of the way every hour
The two cars meet in 12 hours, so the sum of speed is 1 / 12
Therefore, the speed of car B is 1 / 12-1 / 20 = 1 / 30
It takes 30 hours for car B to complete the whole journey
So after meeting, car B has to go: 30-12 = 18 hours

AB is 80 kilometers away from each other. Party A and Party B walk from ab at the same time. After 4 hours of meeting, Party A immediately returns to place a, and Party B goes on. When Party A arrives at place a, Party B is 16 kilometers away from place a

x+y=80/4=20 2*(80-4y)/x=(80-16)/y
x=12
y=8

A and B leave AB at the same time. They meet 40 kilometers away from the destination when they are 5 hours old. A travels 70 kilometers per hour, and B travels how many kilometers per hour?

Let B be x kilometers per hour; in two cases, the first is that B is fast and meets a 40 kilometers past the midpoint;
70×5+40×2=5X
X = 86 km / h
In the second case, B's speed is slow, and it will meet a 40 km away from the midpoint;
70×5-40×2=5X
X = 54 km / h

Freight cars and passenger cars travel from the east to the west at the same time. Freight cars travel 48 kilometers per hour and passenger cars 42 kilometers per hour. The two cars meet at 18 kilometers from the midpoint to find the distance between the East and the West______ Kilometers

18 × 2 △ 48-42 × (48 + 42) = 36 △ 6 × 90, = 6 × 90, = 540 (km). Answer: the distance between the two places is 540 km