For a barrel of oil, 2.4 kilograms are taken out for the first time, and 2/5 is taken out for the second time, and 30% is left. How many kilograms of this barrel of oil are there?
一桶油，第一次取出2.4千克，第二次取出(2/5)，还剩30%，这桶油原来有多少千克？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">1 - (2/5) - (3/10)</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">2.4 / (3/10)</gadget>
<output>8</output>

<result>8</result>