barrel of oil weighs 5 kilograms, pour out (1/2) of the oil for the first time, and pour out (1/2) kilograms for the second time, how many kilograms are left in the barrel.
一桶油重5千克，第一次倒出油的(1/2)，第二次倒出(1/2)千克，桶内还剩多少千克．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">5 * (1/2)</gadget>
<output>5/2 = around 2.5</output>

<gadget id="calculator">5 - (5/2) - (1/2)</gadget>
<output>2</output>

<result>2</result>