A batch of alcohol is placed in two barrels, A and B, neither of which is full. If you pour alcohol from barrel A into barrel B, after barrel B is full, barrel A will have 10 kilograms left; if you pour all the alcohol from barrel B into barrel A, barrel A will hold another 20 kilograms. It is known that the capacity of barrel A is 2.5 times that of barrel B. How many kilograms of this batch of alcohol are there?
一批酒精，放在甲、乙两个桶里，两个桶都未装满．如果把甲桶酒精倒入乙桶，乙桶装满后，甲桶还剩10千克；如果把乙桶酒精全部倒入甲桶后，甲桶还能再盛20千克．已知甲桶的容量是乙桶的2.5倍，这批酒精有多少千克？
<gadget id="calculator">10 + 20</gadget>
<output>30</output>

<gadget id="calculator">2.5 - 1</gadget>
<output>1.5</output>

<gadget id="calculator">30 / 1.5</gadget>
<output>20</output>

<gadget id="calculator">20 + 10</gadget>
<output>30</output>

<result>30</result>