A cylindrical water tank has a bottom area of 20dm**2 and a water depth of 12cm. After a stone is put in, the water level rises to 15cm. What is the volume of the stone?
一口圆柱形水缸，底面积为20dm**2，水深12cm，放进一块石头后水面升到15cm，这块石头的体积是多少？
<gadget id="calculator">15 - 12</gadget>
<output>3</output>

<gadget id="calculator">3 / 10</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">20 * (3/10)</gadget>
<output>6</output>

<result>6</result>