A barrel of oil weighs 40 kg. After pouring out part of the oil, there is still 40% of the oil in the barrel. At this time, the barrel weighs 19.6 kilograms in total. How many kilograms of oil did the barrel originally contain?
一桶油连桶共重40千克．倒出一部分油后，桶里的油还剩40%，这时连桶称共重19.6千克，这个桶原来共装油多少千克？
<gadget id="calculator">40 - 19.6</gadget>
<output>20.4</output>

<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">20.4 / (3/5)</gadget>
<output>34</output>

<result>34</result>