The total weight of a barrel of oil is 100 kg. After pouring out half the barrel of oil, the total weight of the barrel is 60 kg. How much does the barrel of oil weigh?
一桶油连桶共重100千克，倒出半桶油后，连桶共重60千克，这桶油重多少千克．
<gadget id="calculator">100 - 60</gadget>
<output>40</output>

<gadget id="calculator">40 * 2</gadget>
<output>80</output>

<result>80</result>