A bottle of oil weighs 5.1 kg in total, and after half of the oil is poured out, the weight of the bottle is still 2.6 kg. Ask how many kilograms of oil are in the original bottle?
一瓶油连瓶共重5.1千克，倒去一半油后，连瓶还重2.6千克．问原来瓶内装有多少千克油？
<gadget id="calculator">5.1 - 2.6</gadget>
<output>2.5</output>

<gadget id="calculator">2.5 * 2</gadget>
<output>5</output>

<result>5</result>