A barrel of oil is used for the first time (2/5), what fraction of the barrel of oil can be used up for the second time?
一桶油，第一次用去(2/5)，第二次用去这桶油的几分之几才能用完？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

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

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