1. Let x meters per minute, y meters per minute, x >；; Y, then (x-y) × (10/3) = 400, (x+y) × (2/3) = 400, and x = 360m per minute, and y = 240m per minute.

2. Train B is 40km/h, it has been driven for 1.5h, and there is still 300- 1.5x50 = 225, so 225/(40+50) = 2.5h. ..

3. Let the vehicle speed be x, y km/min, 1800=(x+y)× 12, so x+y= 150, and the meeting place is a starting point 1800×(x/x+y).