An unscrupulous vendor cracked down on the banner of "10% off sale of all products" in order to promote products, but in fact the prices of all products were increased by 10% on the basis of the original price, and then sold at 90% of the current price. Has the sales price increased or decreased compared to the original price? What is the magnitude of the change?
某不良商贩为推销商品，打击"所有商品九折销售"的条幅进行宣传，但实际上所有商品的价格都在原价的基础上先上涨了10%，再按现价的90%销售，商品最终的销售价格与原价格比是涨了还是降了？变化幅度是多少？
<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">90 / 100</gadget>
<output>9/10 = around 0.9</output>

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

<gadget id="calculator">1 - (99/100)</gadget>
<output>1/100 = around 0.01</output>

<result>1/100 = around 0.01</result>