A barrel of oil was eaten (1/4) on the first day, and (1/5) was eaten the second time. The first time was 2 kg more than the second time. Ask: How much does this barrel of oil weigh?
一桶油第一天吃掉(1/4)，第二次吃掉(1/5)，第一次比第二次多吃掉了2千克，问：这桶油重多少千克？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

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

<gadget id="calculator">(1/4) - (1/5)</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">2 / (1/20)</gadget>
<output>40</output>

<result>40</result>