For a batch of parts, it takes 5 hours for Master Zhang to complete alone, and 4 hours for Master Li to complete alone. How much less per hour does Master Zhang make than Master Li?
一批零件，张师傅单独做需要5小时完成，李师傅单独做需4小时完成，张师傅每小时比李师傅少做百分之几？
<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>