If the circumference of a cylinder is tripled and the height is doubled, how many times will the volume be doubled?
圆柱的周长扩大3倍，高扩大2倍，则体积扩大多少倍．
<gadget id="calculator">3 ** 2</gadget>
<output>9</output>

<gadget id="calculator">9 * 2</gadget>
<output>18</output>

<result>18</result>