Cut out the largest circle from a rectangle with a length of 3 cm and a width of 2.5 cm, and find the circumference of the circle.
从一张长3厘米、宽2.5厘米的长方形上剪下一个最大的圆形，求这个圆形的周长．
<gadget id="calculator">3.14 * 2.5</gadget>
<output>7.85</output>

<result>7.85</result>