When the selling price of a product is 100 yuan, the profit can be 25%. How much profit can you make if you sell it at 10% off the selling price?
某商品的售价为100元时，可盈利25%．若按售价的九折售出，则可盈利多少元？
<gadget id="calculator">90 / 100</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">100 * (9/10)</gadget>
<output>90</output>

<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 + (1/4)</gadget>
<output>5/4 = around 1.25</output>

<gadget id="calculator">100 / (5/4)</gadget>
<output>80</output>

<gadget id="calculator">90 - 80</gadget>
<output>10</output>

<result>10</result>