In a square with a circumference of 16 decimeters, draw the largest circle, what is the circumference of this circle in decimeters?
在一个周长16分米的正方形里，画一个最大的圆，这个圆的周长是多少分米．
<gadget id="calculator">16 / 4</gadget>
<output>4</output>

<gadget id="calculator">3.14 * 4</gadget>
<output>12.56</output>

<result>12.56</result>