To build a 240-meter-long canal, 80 meters were built in the first 4 days. According to this calculation, how many days will it take to complete the canal?
修一条长240米的水渠，前4天修了80米，照这样计算，修完这条水渠共需多少天？
<gadget id="calculator">80 / 4</gadget>
<output>20</output>

<gadget id="calculator">240 / 20</gadget>
<output>12</output>

<result>12</result>