A barrel of salad oil weighs 5.1 kg even with barrels, and the weight of the barrel is 0.2 kg. How much does the oil weigh in kilograms.
一桶色拉油，连桶共重5.1千克，桶重0.2千克．油重多少千克．
<gadget id="calculator">5.1 - 0.2</gadget>
<output>4.9</output>

<result>4.9</result>