Divide a circle into several equal parts, and then assemble it into an approximate rectangle. If the width of the rectangle is 4 cm, what is its length in cm?
把一个圆平均分成若干份，然后把它拼成一个近似的长方形，如果长方形的宽是4厘米，它的长应是多少厘米．
<gadget id="calculator">2 / 2</gadget>
<output>1</output>

<gadget id="calculator">3.14 * 4 * 1</gadget>
<output>12.56</output>

<result>12.56</result>