Two people, A and B, are running along a 400-meter circular track. They run from the same place with their backs facing each other. After 5 minutes, they face each other 100 meters apart. If A's speed is 5 m/s, what is the minimum speed of B in m/s?
甲、乙二人沿400米环形跑道跑步，二人同时由同一地点背向而行，5分钟后二人迎面相距100米．若甲的速度是5米/秒，那么乙的速度至少是多少米/秒．
<gadget id="calculator">400 / 5 / 60</gadget>
<output>4/3 = around 1.333333</output>

<result>4/3 = around 1.333333</result>