Workers make a batch of parts and complete (2/5) of this batch of parts in 3 days, how many days can they be completed?
工人制作一批零件，3天完成这批零件的(2/5)，多少天可以完成．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

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

<gadget id="calculator">1 / (2/15)</gadget>
<output>15/2 = around 7.5</output>

<result>15/2 = around 7.5</result>