After the price of a product is reduced by 20%, how much should the price be raised again to restore the original price?
某商品降价20%后，要想恢复原价，则要重新提价多少
<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>