It takes four days to complete (1/5) of a project. According to this calculation, how many days will it take to complete half of the whole project.
四天完成一项工程的(1/5)，照这样计算，还要多少天才能完成全工程的一半．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 * (1/2)</gadget>
<output>1/2 = around 0.5</output>

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

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

<gadget id="calculator">(1/2) / (1/20)</gadget>
<output>10</output>

<gadget id="calculator">10 - 4</gadget>
<output>6</output>

<result>6</result>