commodity is first sold at 90% of the original price, and now the price is increased by 10%, what is the current price of the original price?
一种商品，先按原价的90%出售后，现又升价10%，现价是原价的多少．
<gadget id="calculator">90 / 100</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">10 / 100</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 + (1/10)</gadget>
<output>11/10 = around 1.1</output>

<gadget id="calculator">1 * (9/10) * (11/10)</gadget>
<output>99/100 = around 0.99</output>

<result>99/100 = around 0.99</result>