A barrel of oil is 20 liters, now reduced to 16 liters, how much is the reduction
一桶油20升，现减少到16升，减少了多少
<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>