A cylinder and a cone have the same base area and volume, respectively, and the height of the cylinder is 7 centimeters, what is the height of the cone in centimeters?
一个圆柱和一个圆锥体的底面积和体积分别相等，已知圆柱体的高是7厘米，那么圆锥的高是多少厘米．
<gadget id="calculator">7 * 3</gadget>
<output>21</output>

<result>21</result>