Xiaoming's family has a cuboid fish tank. The bottom of the fish tank is a rectangle with a length of 100 cm and a width of 40 cm. A cube stone with a side length of 10 cm is placed inside. How many centimeters will the water level be lowered if the stone is removed?
小明家有一个长方体的鱼缸，鱼缸的底是长为100厘米，宽为40厘米的长方形，里面放置一块棱长为10厘米的正方体石块，向鱼缸里加水，使水面没过石块．如果将石块取出，那么水面降低多少厘米．
<gadget id="calculator">100 * 40</gadget>
<output>4_000</output>

<gadget id="calculator">10 / 4_000</gadget>
<output>1/400 = around 0.0025</output>

<gadget id="calculator">10 * 10 * (1/400)</gadget>
<output>1/4 = around 0.25</output>

<result>1/4 = around 0.25</result>