Draw the largest circle in a square with a perimeter of 20 centimeters, what is its perimeter in centimeters?
在一个周长是20厘米的正方形里画一个最大的圆，它的周长是多少厘米．
<gadget id="calculator">20 / 4</gadget>
<output>5</output>

<gadget id="calculator">3.14 * 5</gadget>
<output>15.7</output>

<result>15.7</result>