In a cylindrical bucket with a base radius of 20 cm, a cylindrical steel material with a radius of 10 cm is immersed in water. When the steel material is removed from the water, the water in the bucket drops by 3 cm. Calculate the value of this steel material long.
在一个底面半径是20厘米的圆柱形水桶里，有一个半径为10厘米的圆柱形钢材浸在水中，当把钢材从水中取走时，桶里的水下降了3厘米，求这段钢材的长．
<gadget id="calculator">20 ** 2</gadget>
<output>400</output>

<gadget id="calculator">10 ** 2</gadget>
<output>100</output>

<gadget id="calculator">3.14 * 100</gadget>
<output>314</output>

<gadget id="calculator">3 / 314</gadget>
<output>3/314 = around 0.009554</output>

<gadget id="calculator">3.14 * 400 * (3/314)</gadget>
<output>12</output>

<result>12</result>