Zhang Hua bought a batch of vegetable oil and put it in barrels A and B, but both barrels were not full. If barrel A is poured into barrel B, and barrel B is full, barrel A will be 10 liters more; if barrel B is poured into barrel A, barrel A will be full by 20 liters. Know that the capacity of bucket A is 2.5 times that of bucket B. How many liters of oil did Zhang Hua buy in total?
张华买了一批菜油，放在A，B两个桶里，两个桶都未能装满．如果把A桶油倒入B桶后，B桶装满，A桶还多10升；如果把B桶倒入A桶，A桶还能再加20升才满．知A桶容量是B桶的2.5倍．问张华一共买了多少升油？
<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>