In a tank with a length of 25 centimeters, a width of 20 centimeters and a height of 30 centimeters, and a water depth of 15 centimeters, a cuboid iron block whose bottom surface is 10 centimeters in length and width and 20 centimeters in height is placed vertically (there is still a section not covered by water. submerged), how many centimeters did the water level rise at this time?
在一个长25厘米、宽20厘米、高30厘米的水槽中，水深15厘米，现垂直放入一个底面长和宽都是10厘米，高是20厘米的长方体铁块(还有一段没有被水淹没)，这时水面上升多少厘米？
<gadget id="calculator">25 * 20</gadget>
<output>500</output>

<gadget id="calculator">10 * 10</gadget>
<output>100</output>

<gadget id="calculator">500 - 100</gadget>
<output>400</output>

<gadget id="calculator">20 / 400</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">15 * 25 * (1/20)</gadget>
<output>75/4 = around 18.75</output>

<gadget id="calculator">(75/4) - 15</gadget>
<output>15/4 = around 3.75</output>

<result>15/4 = around 3.75</result>