Lizhuang needs to build a 1,200-meter canal, and 40% of it will be completed in the first three days. According to this calculation, how many days will it take to complete the canal?
李庄要修一条1200米的水渠，前三天完成40%，照这样计算，修完这条水渠还要多少天？
<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">(2/5) / 3</gadget>
<output>2/15 = around 0.133333</output>

<gadget id="calculator">(3/5) / (2/15)</gadget>
<output>9/2 = around 4.5</output>

<result>9/2 = around 4.5</result>