Divide a circle with a diameter of 16 cm into several equal parts, and then cut and mend it into a rectangle of equal area. What is the length of this rectangle in centimeters?
把直径是16厘米的圆平均分成若干份，然后割补成一个等面积的长方形，这个长方形的长是多少厘米．
<gadget id="calculator">16 / 2</gadget>
<output>8</output>

<gadget id="calculator">3.14 * 8</gadget>
<output>25.12</output>

<result>25.12</result>