If the price of a commodity is increased by 20% first, and then reduced to 80%, the current price is the original price.
一件商品先提价20%，然后再降低到80%，则现在的价格是最初价格的多少．
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 + (1/5)</gadget>
<output>6/5 = around 1.2</output>

<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(4/5) / 1</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 * (6/5) * (4/5)</gadget>
<output>24/25 = around 0.96</output>

<result>24/25 = around 0.96</result>