A barrel of oil is 100 kilograms, pour out 20%, and add another 20%. How much does this barrel of oil weigh now?
一桶油100千克，倒出20%，再增加20%．现在这桶油重多少千克．
<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">100 * (4/5) * (6/5)</gadget>
<output>96</output>

<result>96</result>