The ratio of the perimeter of a square to a circle is 2:1. The side length of the square is 31.4 cm, what is the area of the circle?
一个正方形与一个圆的周长比为2：1．正方形的边长是31.4厘米，圆的面积是多少？
<gadget id="calculator">31.4 / 2</gadget>
<output>15.7</output>

<gadget id="calculator">4 * 15.7</gadget>
<output>62.8</output>

<gadget id="calculator">62.8 / 3.14 / 2</gadget>
<output>10</output>

<gadget id="calculator">10 ** 2</gadget>
<output>100</output>

<gadget id="calculator">3.14 * 100</gadget>
<output>314</output>

<result>314</result>