A wire encloses a circle with a radius of 2 decimeters. If the wire surrounds a square, what is the area of the square?
一根铁丝正好围成一个半径2分米的圆，如果把这根铁丝围成一个正方形，这个正方形的面积是多少平方分米．
<gadget id="calculator">2 / 4</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">2 * 3.14 * (1/2)</gadget>
<output>3.14</output>

<gadget id="calculator">3.14 * 3.14</gadget>
<output>9.8596</output>

<result>9.8596</result>