Two people, A and B, move around a circular field at a constant speed. They start from the two ends of a diameter at the same time and move in opposite directions. When the two meet for the first time, B runs 80 meters. When the two meet for the second time , A is 20 meters away from his starting point, what is the circumference of this circular field in meters? (Pay attention to several situations)
甲、乙两人围绕一个圆形场地做匀速运动，分别从一条直径的两端点同时出发，按相反方向运动，两人第一次相遇时，乙跑了80米，两人第二次相遇时，甲离他出发点20米，求这个圆形场地的周长是多少米？(注意几种情况)
<gadget id="calculator">1.5 / 0.5</gadget>
<output>3</output>

<gadget id="calculator">80 * 3</gadget>
<output>240</output>

<gadget id="calculator">240 + 20</gadget>
<output>260</output>

<gadget id="calculator">260 * 2</gadget>
<output>520</output>

<result>520</result>