A and B are 5km apart, and at the speed of 2km 1 hour and 4km 1 hour. At the same time, a dog runs from a to B at the speed of 12km 1 hour A and B are 5km apart, and at the speed of 2km 1 hour and 4km 1 hour. At the same time, a dog runs from a to B at the speed of 12km 1 hour. When he sees a, he turns to B It's like this until Party A and Party B meet and ask for the distance the dog has run

A and B are 5km apart, and at the speed of 2km 1 hour and 4km 1 hour. At the same time, a dog runs from a to B at the speed of 12km 1 hour A and B are 5km apart, and at the speed of 2km 1 hour and 4km 1 hour. At the same time, a dog runs from a to B at the speed of 12km 1 hour. When he sees a, he turns to B It's like this until Party A and Party B meet and ask for the distance the dog has run

Let X be used
2x+4x=5
6x=5
x=5/6
12x5/6=10（km）

The distance between a and B is 600 km. The fast and slow trains leave from a and B at the same time. They meet 2.5 hours later. It is known that the speed ratio of the fast train to the slow train is 5:3
What's the speed of the express train and the local train

Subconscious sadness,
Speed sum is: 600 △ 2.5 = 240 (km)
Express speed: 240 × 5 / (5 + 3) = 150 (km)
Idle speed: 240 × 3 / (5 + 3) = 90 (km)

The distance between station a and station B is 360 km. The express and local trains start from the two stations at the same time. After 3.6 hours, they meet each other. The speed ratio of fast and slow is 3:2,

Ha, I have math problems every night. I think I should be right. 360km, 3.6 hours, 100 km per hour, the sum of the speed of two cars, and then 2 / 5 times 100, the speed is 40 km per hour