1, let the distance be s km, when the local train is 4s/9 km, the express train is 5s/9 km, and the equation is:

5s/9-4s/9= 15*5

Solution: s=675

So the distance between a and b is 675 kilometers.

2. The speed of A is 440/6=220/3 (km/h) and the speed of B is 440/5=88 (km/h).

T = (440-220/3 *1)/(220/3+88) = 25/1(hour).

So when two cars meet, the distance between A and B is also S = 88 * 25/11= 200 (km).

3. Let A and B do V A and V B every minute, and get the following equation:

(V A +V B) *5=540，V A: V B =5:4。

Solution: V A =60 (km/min), V B =48 (km/min).