If the price of a product is reduced by 20%, then it will be sold with a 10% discount. How much cheaper is the current price of this product than the original price?
一件商品降价20%后再打9折出售，这件商品的现价比原价便宜多少
<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">90 / 100</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">1 * (4/5) * (9/10)</gadget>
<output>18/25 = around 0.72</output>

<gadget id="calculator">1 - (18/25)</gadget>
<output>7/25 = around 0.28</output>

<gadget id="calculator">(7/25) / 1</gadget>
<output>7/25 = around 0.28</output>

<result>7/25 = around 0.28</result>