If the price of a product is reduced by 10% during the promotion period, and then increased by 10% after the promotion, what is the price of the product at this time?
某商品在促销时期降价10%，促销过后又涨10%，这时商品价格是原来价格的多少．
<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">1 + (1/10)</gadget>
<output>11/10 = around 1.1</output>

<gadget id="calculator">(11/10) / 1</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>