A container with a length of 5 decimeters, a width of 4 decimeters, and a height of 2 decimeters is filled with 30 liters of water. How many centimeters is the distance between the water surface and the mouth of the container?
一个长5分米，宽4分米，高2分米的容器里装入30升水，水面离容器口相距多少厘米？
<gadget id="calculator">5 * 4</gadget>
<output>20</output>

<gadget id="calculator">30 / 20</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">2 - (3/2)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(1/2) * 10</gadget>
<output>5</output>

<result>5</result>