In a cuboid tank with a length of 100cm and a width of 80cm, put a cuboid iron block. When the iron block is completely submerged in the water, the water level rises by 4 cm. If the length of the iron block is 40 cm and the width is 20 cm, what is its height in cm?
在一个长100cm，宽80cm的长方体水槽中，放入一个长方体铁块．铁块完全浸入水中时，水面上升了4cm．如果铁块的长是40cm，宽是20cm，它的高是多少厘米？
<gadget id="calculator">40 * 20</gadget>
<output>800</output>

<gadget id="calculator">4 / 800</gadget>
<output>1/200 = around 0.005</output>

<gadget id="calculator">100 * 80 * (1/200)</gadget>
<output>40</output>

<result>40</result>