There is 470 kg of oil in barrel A, and 190 kg of oil in barrel B. How many kilograms of oil in barrel A can be poured into barrel B so that the oil in barrel A is twice the amount of oil in barrel B.
甲桶里有油470千克，乙桶里有油190千克，甲桶的油倒入乙桶多少千克，才能使甲桶油是乙桶油的2倍．
<gadget id="calculator">470 + 190</gadget>
<output>660</output>

<gadget id="calculator">1 + 2</gadget>
<output>3</output>

<gadget id="calculator">660 / 3</gadget>
<output>220</output>

<gadget id="calculator">220 - 190</gadget>
<output>30</output>

<result>30</result>