A sweater is sold at 80%, how much is the current price lower than the original price.
一件羊毛衫按80%出售，现价比原价降低了多少．
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

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

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