There are three barrels A, B, and C. A contains 500 grams of water, B contains 750 grams of 40% brine, and C contains 500 grams of 50% brine. First pour half of the water in A into B, then pour half of the brine in B into C, and then pour half of the brine in C into A, which counts as one round of operation. What is the concentration of brine in bucket A after two rounds of operation? (accurate to one decimal place)
设有甲、乙、丙三个桶，甲中装有500克水，乙中装有浓度为40%的盐水750克，丙中装有浓度为50%的盐水500克．首先将甲中水的一半倒入乙，然后将乙中盐水的一半倒入丙，再将丙中盐水的一半倒入甲，这算进行一轮操作．问进行两轮操作后甲桶中盐水的浓度是多少？(精确到小数点后一位)
<gadget id="calculator">31.1 / 100</gadget>
<output>0.311</output>

<result>0.311</result>