A bottle of oil weighs 6.5 kilograms. After half of the oil is poured out, the weight of the bottle is 3.5 kilograms. How many kilograms does the bottle weigh?
一瓶油连瓶重6.5千克，将油倒出一半后，连瓶重3.5千克，瓶有多重多少千克
<gadget id="calculator">6.5 - 3.5</gadget>
<output>3</output>

<gadget id="calculator">3 * 2</gadget>
<output>6</output>

<gadget id="calculator">6.5 - 6</gadget>
<output>0.5</output>

<result>0.5</result>