A barrel of oil is 5.2 kilograms in total, and after half of it is used, the total weight is 2.7 kilograms. How much does this barrel weigh?
一桶油连桶共5.2千克，用去一半后连通共重2.7千克．这个油桶重多少千克？
<gadget id="calculator">5.2 - 2.7</gadget>
<output>2.5</output>

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

<gadget id="calculator">5.2 - 5</gadget>
<output>0.2</output>

<result>0.2</result>