The two trains leave from a and B at the same time and meet at 48km from the midpoint 4 hours later. It is known that the local train is 37 times the speed of the express train. What are the speeds of the express train and the local train? How many kilometers are there between a and B?

The two trains leave from a and B at the same time and meet at 48km from the midpoint 4 hours later. It is known that the local train is 37 times the speed of the express train. What are the speeds of the express train and the local train? How many kilometers are there between a and B?

Speed of express train: (48 × 2 △ 4) / (1 − 37) = 24 △ 47 = 42 (km) speed of local train: 42 × 37 = 18 (km) distance between a and B: (42 + 18) × 4 = 60 × 4 = 240 (km) answer: speed of express train is 42 km per hour, speed of local train is 18 km per hour, distance between a and B is 240 km

The two trains leave from a and B at the same time and meet at 72 km after 3 hours
It is known that the speed of a slow train is five seventh of that of a fast train. How many kilometers is the distance between a and B? Can you tell us the specific process? Some say 120, some say 864, and some say 432. Which one is correct? Can you explain it carefully?

Take the express train as the unit "1", and the slow train is 5 / 7. The distance between the two trains is 72, which means that the express train has 72 more lines and the slow train has 72 less lines. So 72 + 72 = 144 1-5 / 7 = 2 / 7 (the fast train is more than the slow train). 144 △ 2 / 7 = 504. This is the distance of 3 small lines of the express train, so the slow train is 507 × 5 / 7 = 360.360 + 504 = 864
The elementary school mark application question should use the mark computation to solve