Draw a circle. The distance between the two feet of the compass is 3 cm. What is the circumference of the circle in cm?
画一个圆，圆规两脚间的距离是3厘米，这个圆的周长是多少厘米．
<gadget id="calculator">2 * 3.14 * 3</gadget>
<output>18.84</output>

<result>18.84</result>