There is a barrel of oil, (2/5) is taken out for the first time, and 3 kg more than the first time is taken out for the second time, leaving 21 kg. How many kilograms does this barrel of oil weigh?
有一桶油，第一次取出它的(2/5)，第二次比第一次多取出3千克，还剩21千克．原来这桶油重多少千克？
<gadget id="calculator">3 + 21</gadget>
<output>24</output>

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

<gadget id="calculator">1 - (2/5) - (2/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">24 / (1/5)</gadget>
<output>120</output>

<result>120</result>