A new MP4 is on sale with a 20% discount. The current price is 400 yuan. What is the original price?
一个新款MP4打八折出售，现价400元，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>