The radius of a circular bullpen is 12 meters, how many meters of thick iron wire will be used to surround the bullpen for 3 circles (not counting the joints).
一个圆形牛栏的半径是12米，要用多少米的粗铁丝才能把牛栏围上3圈(接头处不计)．
<gadget id="calculator">2 * 3.14 * 12 * 3</gadget>
<output>226.08</output>

<result>226.08</result>