There is a barrel of oil weighing 24.4 kilograms. Half of the oil is used for the first time, and half of the remaining oil is used for the second time. This is the weight of the barrel of 7 kilograms. How many kilograms of oil are there?
有一桶油重24.4千克，第一次用去一半油，第二次又用去剩下的油的一半，这是连桶重7千克，原来有油多少千克．
<gadget id="calculator">24.4 - 7</gadget>
<output>17.4</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(1/2) * (1/2)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(1/2) + (1/4)</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">17.4 / (3/4)</gadget>
<output>23.2</output>

<result>23.2</result>