If one project takes 4 days to complete (1/5) of the entire project, how many days will it take to complete the rest of the project?
一项工程，4天完成全部工程的(1/5)，照这样计算，完成余下的工程需要多少天．
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(1/5) / 4</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(4/5) / (1/20)</gadget>
<output>16</output>

<result>16</result>