A cylindrical container with a bottom radius of 6 cm, a cylindrical iron rod with a height of 30 cm and a bottom radius of 4 cm is erected in the container (and the iron rod is in full contact with the bottom surface of the container). At this time, the water depth in the container is 20 cm , Now lift the iron rod up slightly by 8cm, how many centimeters will the water drop at this time?
一个圆柱体容器，底面半径为6厘米，容器里直立着一根高为30cm，底面半径为4cm的圆柱体铁棒(且铁棒与容器的底面充分的接触)，这时容器里的水深20cm，现在把铁棒轻轻地向上提起8cm，那么这时水会下降多少厘米？
<gadget id="calculator">6 ** 2</gadget>
<output>36</output>

<gadget id="calculator">3.14 * 36 * 20</gadget>
<output>2_260.8</output>

<gadget id="calculator">4 ** 2</gadget>
<output>16</output>

<gadget id="calculator">3.14 * 16 * 8</gadget>
<output>401.92</output>

<gadget id="calculator">2_260.8 - 401.92</gadget>
<output>1_858.88</output>

<gadget id="calculator">3.14 * 36</gadget>
<output>113.04</output>

<gadget id="calculator">1_858.88 / 113.04</gadget>
<output>16.444444</output>

<gadget id="calculator">20 - 16.444444</gadget>
<output>3.555556</output>

<result>3.555556</result>