cylindrical small bucket filled with water with a bottom radius of 20 cm contains a cylindrical steel material with a diameter of 10 cm immersed in water. When the steel material is removed from the bucket, the water in the bucket drops by 3 cm. Find The length of this section of steel.
一个装有水的底面半径为20厘米的圆柱形小桶，内有一块直径为10厘米的圆柱形钢材浸在水中，当钢材从桶里取走后，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">3.14 * 400 * 3</gadget>
<output>3_768</output>

<gadget id="calculator">10 / 2</gadget>
<output>5</output>

<gadget id="calculator">5 ** 2</gadget>
<output>25</output>

<gadget id="calculator">3.14 * 25</gadget>
<output>78.5</output>

<gadget id="calculator">3_768 / 78.5</gadget>
<output>48</output>

<result>48</result>