A barrel of gasoline is 4 kilograms lighter than a barrel of kerosene, which is 1/5 lighter than this barrel of kerosene. How many kilograms is this barrel of kerosene?
一桶汽油比一桶煤油轻4千克，比这桶煤油轻(1/5)，这桶煤油多少千克？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

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

<result>20</result>