In a cylindrical water tank with a radius of 20 cm, there is a section of square steel submerged in water, and the side length of the square is 4 cm. When this section of square steel was taken out of the water, the water in the bucket dropped by 0.5 cm. How many centimeters is this piece of square steel?
在半径为20厘米的圆柱形储水桶里，有一段截面为正方形的方钢浸没在水中，正方形的边长是4厘米．当这段方钢从水中取出时，桶里的水而下降了0.5厘米．这段方钢长多少厘米？
<gadget id="calculator">20 ** 2</gadget>
<output>400</output>

<gadget id="calculator">3.14 * 400 * 0.5</gadget>
<output>628</output>

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

<gadget id="calculator">628 / 16</gadget>
<output>157/4 = around 39.25</output>

<result>157/4 = around 39.25</result>