A glass tank has a bottom area of 15 square decimeters and a water depth of 15 cm. After a stone is put in, the water rises to 18 cm. What is the volume of the stone?
一只玻璃缸，底面积15平方分米，水深15厘米，放进一块石头后水面升到18厘米，这块石头体积是多少？
<gadget id="calculator">18 - 15</gadget>
<output>3</output>

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

<gadget id="calculator">15 * (3/10)</gadget>
<output>9/2 = around 4.5</output>

<result>9/2 = around 4.5</result>