A barrel of oil weighs 6 kilograms. After half of it is used up, the weight of the barrel is 3.05 kilograms. How many kilograms does the barrel of oil weigh?
一桶油连桶重6千克，用去一半后，连桶重3.05千克，这桶油重多少千克．
<gadget id="calculator">6 - 3.05</gadget>
<output>2.95</output>

<gadget id="calculator">2.95 * 2</gadget>
<output>5.9</output>

<result>5.9</result>