There is a barrel of oil, 20% of which is used for the first time, and the whole barrel (2/5) is used for the second time, and 6 kg is used for the two times. How many kilograms does this barrel of oil weigh?
有一桶油，第一次用去20%，第二次又用去全桶的(2/5)，两次共用去6千克，这桶油重多少千克？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

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

<gadget id="calculator">6 / (3/5)</gadget>
<output>10</output>

<result>10</result>