Example 5: Two people, A and B, are running along the track of the sports field. A runs 290 meters per minute, and B runs 270 meters per minute. The length of one lap of the track is 400 meters. If two people run in the same direction from the starting line at the same time, how long will it take for A to catch up with B for the first time?
例5：甲、乙二人沿运动场的跑道跑步，甲每分钟跑290米，乙每分钟跑270米，跑道一圈长400米．如果两人同时从起跑线上同方向跑，那么甲经过多长时间才能第一次追上乙？
<gadget id="calculator">290 - 270</gadget>
<output>20</output>

<gadget id="calculator">400 / 20</gadget>
<output>20</output>

<result>20</result>