The diameter of a circular flower bed is 12m, and there is a guardrail around the perimeter, how many meters is the length of the guardrail?
一个圆形花坛的直径是12m，沿着周长围一圈护栏，护栏的长是多少米？
<gadget id="calculator">3.14 * 12</gadget>
<output>37.68</output>

<result>37.68</result>