Pour (1/6) of the oil in barrel A into barrel B. At this time, the two barrels have the same amount of oil. It turns out that the oil in barrel B is the amount of oil in barrel A
把甲桶油的(1/6)倒入乙桶，这时两桶油一样多．原来乙桶油是甲桶油的多少
<gadget id="calculator">1 / 6</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">1 - (1/6) - (1/6)</gadget>
<output>2/3 = around 0.666667</output>

<result>2/3 = around 0.666667</result>