A cylindrical cup with a bottom diameter of 20cm, the height of the water in the cup is 20cm, just as high as the conical plumb weight with a bottom diameter of 6cm placed in the water, how many centimeters will the water in the cup drop after taking out the plumb bob?
一个底面内直径20cm的圆柱杯，杯中水面高20cm，正好和水中放着的底面直径为6cm的圆锥铅锤一样高，取出铅锤后，杯中的水下降几厘米？
<result>0.6</result>