If the working hours of workers in a workshop remain the same, if the number of workers is reduced by 20%, how much must the work efficiency be increased to keep the output unchanged?
某车间工人的工作时间保持不变，如果工人人数减少20%，要保持产量不变，工作效率要提高多少．
<gadget id="calculator">20 / 100</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) / (4/5)</gadget>
<output>1/4 = around 0.25</output>

<result>1/4 = around 0.25</result>