A barrel of oil weighs 2 kilograms. After pouring out (1/5) of it, pour out another (1/5) kilogram. How many kilograms of oil is less than the original one?
一桶油重2千克，倒出它的(1/5)后，又倒出(1/5)千克，这通油比原来少了多少千克．
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">2 * (1/5)</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(2/5) + (1/5)</gadget>
<output>3/5 = around 0.6</output>

<result>3/5 = around 0.6</result>