A commodity whose price is increased by 30% first, and then reduced by 30%, what is the price of this commodity?
一种商品，先涨价30%，后降价30%，这种商品的价格是原价的多少．
<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 + (3/10)</gadget>
<output>13/10 = around 1.3</output>

<gadget id="calculator">1 - (3/10)</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">(13/10) * (7/10)</gadget>
<output>91/100 = around 0.91</output>

<result>91/100 = around 0.91</result>