A commodity is sold for 99 yuan after a 10% price reduction and then a 10% price increase. What is the original price of this commodity?
一种商品，先降价10%后，又涨价10%后卖99元，这件商品的原价是多少？
<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 - (1/10)</gadget>
<output>9/10 = around 0.9</output>

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

<result>100</result>