If (1/5) of a job can be completed in 4 hours, how many hours will it take to complete the job?
一项工作如果4小时可以完成它的(1/5)，那么完成这项工作需多少小时．
<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 / (1/20)</gadget>
<output>20</output>

<result>20</result>