A wire encloses a square with a circumference of 16 decimeters. If this wire forms a circle, what is the area of the circle?
一根铁丝正好围成一个周长为16分米的正方形，如果把这根铁丝围成一个圆，这个圆的面积是多少．
<gadget id="calculator">16 / 3.14 / 2</gadget>
<output>2.547771</output>

<gadget id="calculator">2.547771 ** 2</gadget>
<output>6.491137</output>

<gadget id="calculator">3.14 * 6.491137</gadget>
<output>20.38217</output>

<result>20.38217</result>