A barrel of oil weighs 10 kilograms. After half of the oil is used, the weight of the barrel is 5.5 kilograms. How many kilograms does the barrel weigh?
一桶油连桶重10千克，用去一半油后连桶重5.5千克，桶重多少千克？
<gadget id="calculator">5.5 - 4.5</gadget>
<output>1</output>

<result>1</result>