Wang Qiang and Liu Ying are running on a circular track with a circumference of 400m. Wang Qiang runs 5m per second. Liu Ying runs 3m per second. They start from the same place at the same time and run in opposite directions. So how long did it take for the two to meet for the first time?
王强和刘英在周长为400m的环形跑道上跑步，王强每秒跑5m．刘英每秒跑3m，他们从同一地点同时出发，反向而跑．那么二人从出发到第一次相遇需多长时间？
<gadget id="calculator">5 + 3</gadget>
<output>8</output>

<gadget id="calculator">400 / 8</gadget>
<output>50</output>

<result>50</result>