The price of a commodity is increased by 25% first, and then the price is reduced by a certain amount, so that the current price is equal to the original price.
一种商品先提价25%后，又降价多少，现价与原价相等．
<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

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

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

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

<gadget id="calculator">(1/4) / (5/4)</gadget>
<output>1/5 = around 0.2</output>

<result>1/5 = around 0.2</result>