The distance from city a to city B is 240 kilometers. When a truck goes there, it travels 60 kilometers per hour. When it returns by the same way, it travels 40 kilometers per hour The average speed of the truck to and from ab

The distance from city a to city B is 240 kilometers. When a truck goes there, it travels 60 kilometers per hour. When it returns by the same way, it travels 40 kilometers per hour The average speed of the truck to and from ab

The speed is 240 km / 60 km = 4 hours
The return speed is: 240 km / 40 km = 6 hours
Therefore, the average speed of the two trucks to and from ab city is (240 km * 2) / (4 hours + 6 hours) = 48 km / h

A. B is 1200 meters apart. A starts from a and B from B at the same time. A travels 50 meters per minute and B 70 meters per minute. They meet at C for the first time. What's the distance between AC? If two people continue to move forward after meeting, return immediately after arriving at a and B, and meet at d for the second time, what is the distance between CD?

(1) 50:70 = 5:71200 × 55 + 7 = 500 (m); answer: the distance between AC is 500 m (2) 500 × 3-1200 = 300 (m), 1200-500-300 = 400 (m); answer: the distance between CD is 400 m