6. The track of the sports ground is 400 meters long. A practice cycling, riding an average of 350 m per minute; B practiced running, averaging 250m per grid. How long does it take for two people to meet for the first time from the same place and in the opposite direction at the same time? How long did it take to meet again?

Solution: suppose we meet for the first time after X.

350x+250x=400

600x=400

x=2/3。

Because A and B are driving at the same speed, they meet every 2/3 minutes.

A: We met for the first time after 2/3 minutes, and then we met again after 2/3 minutes.