For a project, 60% of it is completed in 3 days, and how many days will it take to complete the rest.
一项工程，3天完成它的60%，余下的还要多少天完成．
<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(2/5) / (1/5)</gadget>
<output>2</output>

<result>2</result>