Fill a cuboid water tank with a length of 3 decimeters and a width of 2 decimeters to a height of 12 centimeters, and then put a cuboid iron block with a bottom area of 120 square centimeters into the water tank vertically, so that the bottom surface of the iron block is in close contact with the bottom surface of the water tank (no The water overflows), but the iron block still partially protrudes from the water surface. How many centimeters does the water in the water tank rise from before?
在一个长3分米、宽2分米的长方体水箱内装水12厘米高，再将一个底面积为120平方厘米的长方体铁块竖直放入水箱，让铁块底面与水箱底面紧密接触(无水溢出)，但铁块仍有部分露出水面，水箱内的水比原先升高了多少厘米？
<gadget id="calculator">3 * 10</gadget>
<output>30</output>

<gadget id="calculator">2 * 10</gadget>
<output>20</output>

<gadget id="calculator">30 * 20</gadget>
<output>600</output>

<gadget id="calculator">600 - 120</gadget>
<output>480</output>

<gadget id="calculator">12 / 480</gadget>
<output>1/40 = around 0.025</output>

<gadget id="calculator">120 * (1/40)</gadget>
<output>3</output>

<result>3</result>