Total speed: 320÷2= 160 (km/h)

A speed: (160+40)÷2= 100 (km/h)

Speed B: 100-40=60 (km/h)

2.107/15 ÷ (1/3 ÷ 2) = 62.8 (m)

3. 100÷(5-4)= 100 (seconds) Join without rest, and it will take 100 seconds to catch up.

100× 5 ÷100-1= 4 (times) This is the number of times A has rested.

4× 10, this is the rest time.

100+10× 4 =140 (seconds) to catch up.

4. When two people meet at the starting point, the running distance must be a multiple of 40, and the running distance of A is 6/4 times that of B ... So B ran at least 80 meters, and A ran at least 120 meters.

At this time, the two men ran 80÷÷4 = 20 (seconds).

And two people meet once every 40 minutes (4+6) = 4 seconds.

20÷4=5 (times) meet five times, and then subtract the last time.

Equal to * * * met four times on the road.