The circumference of a circular lotus pond is 400 meters. A and B run clockwise around the lotus pond. A runs 250 meters per minute, and B runs 200 meters per minute. Now A is 50 meters behind B. How many minutes later will A and B meet?
一个圆形荷花池的周长为400米，甲、乙两人绕荷花池顺时针跑步，甲每分钟跑250米，乙每分钟跑200米，现在甲在乙后面50米，多少分钟后甲乙相遇？
<gadget id="calculator">400 + 50</gadget>
<output>450</output>

<gadget id="calculator">250 - 200</gadget>
<output>50</output>

<gadget id="calculator">450 / 50</gadget>
<output>9</output>

<result>9</result>