A barrel of oil, 20 kg is taken out for the first time, and (2/5) of this barrel of oil is taken out for the second time, and there is still 40 kg left in the barrel. How many kilograms does this barrel of oil weigh?
一桶油，第一次取出20千克，第二次取出这桶油的(2/5)，桶里还剩下40千克，这桶油重多少千克？
<gadget id="calculator">20 + 40</gadget>
<output>60</output>

<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>

<gadget id="calculator">60 / (3/5)</gadget>
<output>100</output>

<result>100</result>