A piece of iron wire is 20 meters long, if 20% of the total length is cut off, what is left?
一根铁丝长20米，剪去全长的20%，还剩多少．
<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">20 * (4/5)</gadget>
<output>16</output>

<result>16</result>