There is a barrel of oil, 20% is used for the first time, 2.4 kg is used for the second time, and 1.6 kg is left. How many kilograms does this barrel of oil weigh?
有一桶油，第一次用去20%，第二次用去2.4千克，还剩1.6千克．这桶油重多少千克？
<gadget id="calculator">2.4 + 1.6</gadget>
<output>4</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">4 / (4/5)</gadget>
<output>5</output>

<result>5</result>