A barrel of oil weighs 56.2 kilograms. After half of the oil is used, the weight of the barrel is 30.2 kilograms. How many kilograms does the oil barrel weigh?
一桶油连桶重56.2千克，用去一半油后，连桶重30.2千克，油桶重多少千克？
<gadget id="calculator">56.2 - 30.2</gadget>
<output>26</output>

<gadget id="calculator">30.2 - 26</gadget>
<output>4.2</output>

<result>4.2</result>