Teacher Xu wants to use wire to surround a circle with a radius of 5cm. What is the minimum length of wire she needs to use?
徐老师要用铁丝围一个半径是5cm的圆，她至少要用多长的铁丝？
<gadget id="calculator">3.14 * 5 * 2</gadget>
<output>31.4</output>

<result>31.4</result>