A barrel of oil has 3 kilograms. If you take out 2/5 kg from the barrel, there is still 3-2/5 = 2.6 kg left in the barrel.

Pour into barrel B. At this time, the two barrels of oil are equally heavy, indicating that barrel B has 2.6 kilograms after pouring out.

Take out 2/5 kg from barrel A, pour it into barrel B,

So the original barrel B has: 2.6-2/5 = 2.2kg..

2. Similar to the above question. Only the percentage is poured out.

A barrel of oil has 3 kilograms, so take out 2/5 from the barrel, so take it out:

3 * 2/5 = 1.2kg。

Then there's only one bucket left.

: 3-1.2 =1.8kg.

Pour into barrel B. At this time, the two barrels of oil are equally heavy, which means that barrel B also has1.8kg.

Take out 2/5 (i.e. 1.2kg) from barrel A and pour it into barrel B,

So the original barrel b has:

1.8- 1.2 = 0.6kg。