A cylindrical bucket with a bottom diameter of 40cm contains a steel rod with a length of 12cm in the water. When the steel rod (1/3) is taken out, the water drops by 0.25cm. Find the diameter of the steel rod?
一只底直径40cm的圆柱形水桶，水里有一根长12cm的钢条，取出钢条(1/3)时，水下降0.25cm，求钢条的直径？
<gadget id="calculator">5 * 2</gadget>
<output>10</output>

<result>10</result>