Existing A has 3 kilograms of pure alcohol, and B has 2 kilograms of pure water. Take a kilogram from A and pour it into the cup of B. After stirring evenly, take a kilogram from B to the cup of A. At this time, the pure water of A is more than the alcohol of B. How many kilograms.
现有甲3千克纯酒精，乙2千克纯水，从甲取a千克倒入乙杯，搅拌均匀后，再从乙取a千克到甲杯，这时，甲的纯净水比乙的酒精多多少千克．
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