A circular runway is 400 meters long. If one billboard is erected every 20 meters, how many billboards can be erected in total?
一个圆形跑道长400米，如果每20米竖一个广告牌，一共可以竖多少个．
<gadget id="calculator">400 / 20</gadget>
<output>20</output>

<result>20</result>