Answer: Because A is faster than B, when A catches up with B, A runs one lap more than B..
So time =400/(5-3)=200 seconds.
2。 If two people start in opposite directions at the same time, it will be the first time to meet each other in a few seconds.
Answer: 400/(5+3)=50 seconds.
3. After B's first departure 10 seconds, A chases B in the direction of B's departure, and after a few seconds, A is required to catch up with B for the first time.
Answer: If the time is X, then 5X=3X+3x 10 X= 15.
4. The distance between Party A and Party B is100m. Party A and Party B are required to set out in the same place and direction at the same time (A is before B) and meet for the first time after a few seconds.
400/(5-3)-100/(5-3) =150 seconds