A barrel of oil is 20L, and 16L is left after using part of it. What percentage of the barrel of oil is used?
一桶油20L，用了一部分后还剩下16L，用了这桶油的百分之几？
<gadget id="calculator">20 - 16</gadget>
<output>4</output>

<gadget id="calculator">4 / 20</gadget>
<output>1/5 = around 0.2</output>

<result>1/5 = around 0.2</result>