What is the circumference of the circle drawn when the distance between the feet of the compass is 2.5 cm?
当圆规两脚间的距离是2.5厘米时，画成的圆的周长是多少．
<gadget id="calculator">2 * 3.14 * 2.5</gadget>
<output>15.7</output>

<result>15.7</result>