There is a circular fish pond in the children's park. Two rounds of circular railings with a diameter of 15m should be made around the fish pond. How many meters of steel bars should be used at least?
儿童公园有一个圆形鱼池，在鱼池的周围要做2圈直径是15m的圆形栏杆，至少要用钢条多少米？
<gadget id="calculator">2 * 3.14 * 15</gadget>
<output>94.2</output>

<result>94.2</result>