The oil in barrel A is 3.6 kg more than that in barrel B. If 1 kg is taken out from each of the two barrels, the oil left in barrel A (2/21) is equal to the oil left in barrel B (1/7). So how many kilograms of original oil is in barrel A?
甲桶油比乙桶油多3.6千克，如果从两桶中各取出1千克后，甲桶里剩下油的(2/21)等于乙桶里剩下油的(1/7)．那么甲桶原有油多少千克？
<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">(1/7) * 3.6</gadget>
<output>0.514286</output>

<gadget id="calculator">2 / 21</gadget>
<output>2/21 = around 0.095238</output>

<gadget id="calculator">(1/7) - (2/21)</gadget>
<output>1/21 = around 0.047619</output>

<gadget id="calculator">0.514286 + (1/21)</gadget>
<output>0.561905</output>

<gadget id="calculator">0.561905 / (1/21)</gadget>
<output>11.800005</output>

<result>11.800005</result>