There is a cuboid glass tank with a length of 1.8 decimeters, a width of 1.3 decimeters, and a water depth of 0.8 decimeters. After putting in 3 earth and rocks, the water level rose to 12 cm. What is the average cubic decimeter volume of each rock?
有一个长方体玻璃缸，长1.8分米、宽1.3分米、水深0.8分米．放入3个土石后，水面上升到12厘米．平均每个土石的体积是多少立方分米？
<gadget id="calculator">12 / 10</gadget>
<output>6/5 = around 1.2</output>

<gadget id="calculator">(6/5) - 0.8</gadget>
<output>0.4</output>

<gadget id="calculator">0.4 / 3</gadget>
<output>0.133333</output>

<gadget id="calculator">1.8 * 1.3 * 0.133333</gadget>
<output>0.311999</output>

<result>0.311999</result>