In a cylinder with a base radius of 30cm, there is a steel cylinder with a length of 18cm completely submerged in water. After the steel is taken out of the water, the water in the bucket drops by 2 cm. What is the diameter of the bottom of the steel in centimeters?
一个底面半径是30cm的圆柱形里，有一段长18cm的圆柱形钢材完全浸没在水中．把钢材从水中取出后，桶里的水下降了2cm，这段钢材的底面直径是多少厘米？
<gadget id="calculator">2 * 10</gadget>
<output>20</output>

<result>20</result>