To build a road with a length of 720 meters, 400 meters in the first 5 days, according to this calculation, how many days will it take to complete the road? (Solution by ratio).
修一条长720米的公路，前5天400米，照这样计算，修完这条公路需要多少天？(用比例解)．
<gadget id="calculator">400 / 5</gadget>
<output>80</output>

<gadget id="calculator">720 / 80</gadget>
<output>9</output>

<result>9</result>