There is a cylinder and a cone of equal volume. The height of the cone is 9 cm and the area of the base is twice that of the cylinder. What is the height of the cylinder?
有一个圆柱体和圆锥体的体积相等．圆锥体的高是9厘米、底面积是圆柱体的2倍，那么，圆柱体的高是多少．
<result>6</result>