If the area of a semicircle is 18π, what is the perimeter of the semicircle?
如果一个半圆形的面积是18π，则这个半圆形的周长是多少．
<gadget id="calculator">3.14 * 6</gadget>
<output>18.84</output>

<gadget id="calculator">6 * 2</gadget>
<output>12</output>

<gadget id="calculator">18.84 + 12</gadget>
<output>30.84</output>

<result>30.84</result>