circular runway is 400 meters long. Xiaoqiang runs 300 meters per minute, and Xiaoxing runs 250 meters per minute. The two start at the same time at the same time. How long did it take for Xiaoqiang to catch up with Xiaoxing for the first time?
一条环形跑道长400米，小强每分钟跑300米，小星每分钟跑250米，两人同时同地同向出发，经过多长时间小强第一次追上小星？
<gadget id="calculator">300 - 250</gadget>
<output>50</output>

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

<result>8</result>