If the selling price of a commodity increases (1/20) from the purchase price, then the purchase price is less than the selling price.
某商品卖出价比进货价增加(1/20)，则进货价比卖出价少多少．
<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">1 + (1/20)</gadget>
<output>21/20 = around 1.05</output>

<gadget id="calculator">(1/20) / (21/20)</gadget>
<output>1/21 = around 0.047619</output>

<result>1/21 = around 0.047619</result>