A barrel of oil is 6 kilograms, 40% is used, how many kilograms are left?
一桶油6千克，用去40%，还剩多少千克．
<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

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

<gadget id="calculator">6 * (3/5)</gadget>
<output>18/5 = around 3.6</output>

<result>18/5 = around 3.6</result>