A barrel of diesel oil weighs 640 kilograms. After half of it is used up, the weight of the barrel is 360 kilograms. How many kilograms does the oil barrel weigh?
一桶柴油连桶重640千克，用掉一半后，连桶重360千克，油桶重多少千克？
<gadget id="calculator">640 - 360</gadget>
<output>280</output>

<gadget id="calculator">280 * 2</gadget>
<output>560</output>

<gadget id="calculator">640 - 560</gadget>
<output>80</output>

<result>80</result>