There are 500 air conditioners, and after selling 20% of them, add another 20%, how many air conditioners are there at this time?
有500台空调，卖掉20%后，再增加20%，这时空调有多少台．
<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 + (1/5)</gadget>
<output>6/5 = around 1.2</output>

<gadget id="calculator">500 * (4/5) * (6/5)</gadget>
<output>480</output>

<result>480</result>