The unit price of a commodity is raised first, and then dropped by 20% to return to the original price. How much has the unit price of this item increased.
某商品单价先上调，再下降20%才能降回原价．该商品单价上调了多少．
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - 1</gadget>
<output>0</output>

<gadget id="calculator">(1/5) + 0</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">(1/5) / (4/5)</gadget>
<output>1/4 = around 0.25</output>

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