Xiaoying bought a new piano for 8,100 yuan on Children's Day on June 1st. My mother told others: "I bought this piano after the price was reduced by 10%." Do you know how much this piano originally sold for?
"六一"儿童节小英家用8100元买了一架新钢琴．妈妈告诉别人说："这架钢琴降价10%后我才买的．"你知道这架钢琴原来卖多少元吗？
<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">8_100 / (9/10)</gadget>
<output>9_000</output>

<result>9_000</result>