The diameter of a circular flower bed is 12m. If a gravel road is built around it, how many meters is the length of the gravel road?
一个圆形花坛的直径是12m，如果在其周围修就条石子路，石子路大约长多少m．
<gadget id="calculator">3.14 * 12</gadget>
<output>37.68</output>

<result>37.68</result>