The original price of a commodity is 400 yuan, and now it is sold at a 10% discount. How much is the current price cheaper than the original price?
一种商品原价400元，现按九折出售，现在的价格比原来便宜多少元
<gadget id="calculator">90 / 100</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">1 - (9/10)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">400 * (1/10)</gadget>
<output>40</output>

<result>40</result>