A bottle of oil weighs 3.8 kilograms. After half of it is used, the bottle still weighs 2.2 kilograms. How many kilograms of oil are there?
一瓶油连瓶重3.8千克，用去一半后，连瓶还重2.2千克，原来有油多少千克．
<gadget id="calculator">3.8 - 2.2</gadget>
<output>1.6</output>

<gadget id="calculator">1.6 * 2</gadget>
<output>3.2</output>

<result>3.2</result>