It took 4 days (1/4) to build a canal with a length of 1600 meters. According to this calculation, how many days will it take to complete the canal?
修一条长1600米的水渠，实际4天修了(1/4)，照这样计算，修完这条水渠还需几天？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">4 / (1/4)</gadget>
<output>16</output>

<gadget id="calculator">16 - 4</gadget>
<output>12</output>

<result>12</result>