Let the train speed be X, the speed of Party A and Party B be Y, and the train length be M. ..

Because it takes longer for the train to pass through A than B, the train and A move in the same direction, but in opposite directions.

And:

6(x-y)=m

5(x+y)=m

Solution:

x= 1 1m/60

y=m/60

The distance that the train travels in 4 minutes (240 seconds) is: (1 1m/60)*240=44m.

A The distance traveled in 4 minutes (240 seconds) is (m/60)*240=4m.

Therefore, when the train meets B four minutes later, the distance between Party A and Party B is 44m-4m=40m.

Therefore, they need 40 m/[(m/60)+(m/60)] to meet.

= 40m/(m /30)

= 1200 seconds =20 minutes.