A product, after the first price reduction (1/10), no one cares about it. In order to promote sales, the shopkeeper lowered the price (1/10) on this basis. The current price is the original price.
一件商品，第一次降价(1/10)后无人问津．店主为了促销，在此基础上又降价(1/10)，现在的价格是原价的多少．
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 - (1/10)</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">(9/10) * (9/10)</gadget>
<output>81/100 = around 0.81</output>

<result>81/100 = around 0.81</result>