Someone bought a stock at the beginning of the year, and the stock fell by 20% that year, how much should it rise in the second year to maintain its original value?
某人年初买了一种股票，该股票当年下跌了20%，第二年应上涨多少才能保持原值？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

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

<gadget id="calculator">(5/4) - 1</gadget>
<output>1/4 = around 0.25</output>

<result>1/4 = around 0.25</result>