Draw the largest circle in a square with a circumference of 28 cm. What is the circumference of the circle in cm?
在一个周长是28厘米的正方形里画一个最大的圆，圆的周长是多少厘米．
<gadget id="calculator">28 / 4</gadget>
<output>7</output>

<gadget id="calculator">3.14 * 7</gadget>
<output>21.98</output>

<result>21.98</result>