A certain shirt is on sale, and the price is reduced twice in a row, each time the price is reduced by 10%. At this time, buying this shirt is cheaper than selling it at the original price by how many percent?
某种衬衫做促销，连续降价两次，每次都降价10%，此时买这种衬衫比按原价卖便宜了百分之几？
<gadget id="calculator">10 / 100</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>

<gadget id="calculator">1 - (81/100)</gadget>
<output>19/100 = around 0.19</output>

<result>19/100 = around 0.19</result>