After an empty barrel is filled with 40% oil, the weight of the barrel is 8.5kg. When the barrel is full of oil, the weight of the barrel is 16kg. How much oil can this barrel hold?
一个空桶装进40%的油后，连桶重8.5kg，当油桶装满油后连桶重16kg，这个油桶共可装油多少kg？
<gadget id="calculator">16 - 8.5</gadget>
<output>7.5</output>

<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">7.5 / (3/5)</gadget>
<output>12.5</output>

<result>12.5</result>