Put a stone in a glass tank with a length of 50 cm and a width of 30 cm. The stone is submerged in water. At this time, the water depth is 20 cm. After the stone is taken out, the water depth is 15 cm. What is the volume of the stone in cubic decimeters?
在一个长50cm，宽30cm的玻璃缸中放入一块石块，石块浸没在水中，这时水深20cm，取出石块后水深15cm，石块的体积是多少立方分米？
<gadget id="calculator">20 - 15</gadget>
<output>5</output>

<gadget id="calculator">5 / 1_000</gadget>
<output>1/200 = around 0.005</output>

<gadget id="calculator">50 * 30 * (1/200)</gadget>
<output>15/2 = around 7.5</output>

<result>15/2 = around 7.5</result>