A product is priced at 400 yuan after a 20% discount. What is the original price of this product?
一件商品打八折后售价400元，这件商品的原价是多少元．
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">400 / (4/5)</gadget>
<output>500</output>

<result>500</result>