A barrel of oil weighs 72 kilograms. After half of the oil is used, the weight of the barrel is 38 kilograms. How many kilograms does the crude oil in the barrel weigh?
一桶油连桶重72千克，用去一半油后，连桶重38千克，这桶内原油重多少千克．
<gadget id="calculator">72 - 38</gadget>
<output>34</output>

<gadget id="calculator">34 * 2</gadget>
<output>68</output>

<result>68</result>