To build a 180-meter-long embankment, it takes 2 days to build 40 meters. According to this calculation, how many days will it take to complete the whole process? (Solution by proportional method)
要修一条长180米的堤坝，用2天就修了40米，照这样计算，修完全程要多少天完成？(用比例方法解)
<gadget id="calculator">40 / 2</gadget>
<output>20</output>

<gadget id="calculator">180 / 20</gadget>
<output>9</output>

<result>9</result>