If a circle with a diameter of 4 cm is divided into several equal parts, what is the perimeter of the approximate rectangle in cm?
把一个直径是4厘米的圆分成若干等份，拼成的近似长方形的周长为多少厘米．
<gadget id="calculator">3.14 * 4</gadget>
<output>12.56</output>

<gadget id="calculator">12.56 + 4</gadget>
<output>16.56</output>

<result>16.56</result>