Knead a cone of plasticine with a height of 21 cm into a cylinder with the same base area. What is the height of the cylinder in cm?
把一块高21cm的圆锥体橡皮泥捏成一个底面积相等的圆柱体，圆柱体的高是多少cm．
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">21 * (1/3)</gadget>
<output>7</output>

<result>7</result>