There is 10.8 kilograms of water in the big bucket, and after pouring 2.2 kilograms of water into the small bucket, the big bucket weighs the same as the water in the small bucket. How many kilograms of water are there in the small bucket?
大桶里有10.8千克水，倒入小桶里2.2千克水后，大桶和小桶里的水一样重，小桶里原来有水多少千克？
<gadget id="calculator">2.2 * 2</gadget>
<output>4.4</output>

<gadget id="calculator">10.8 - 4.4</gadget>
<output>6.4</output>

<result>6.4</result>