The sum of the volumes of a cylinder and a cone with the same base and height is 28 cubic meters, what is the volume of the cylinder in cubic meters
等底等高的圆柱体和圆锥体体积之和是28立方米，圆柱体的体积是多少立方米
<gadget id="calculator">28 / 4</gadget>
<output>7</output>

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

<result>21</result>