A piece of work is completed by A alone in 5 hours and by B in 4 hours, how much slower is A's work efficiency than B's work efficiency.
一件工作单独由甲做5小时完成，由乙做4小时完成，甲的工效比乙工效慢多少．
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

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

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

<gadget id="calculator">(1/20) / (1/4)</gadget>
<output>1/5 = around 0.2</output>

<result>1/5 = around 0.2</result>