There is a circular goldfish pond with a diameter of 15 meters in the children's park. To make 2 circles of circular railings around the goldfish pond, how long should the steel bars be at least?
儿童公园有一个直径是15米的圆形金鱼池，在金鱼池周围要做2圈圆形栏杆，至少要用多长钢条？
<gadget id="calculator">3.14 * 15 * 2</gadget>
<output>94.2</output>

<result>94.2</result>