Cut out the largest circle from a rectangular piece of paper with a length of 30 cm and a width of 20 cm. What is the area of this circle in square centimeters?
从一个长30厘米，宽20厘米的长方形纸片中，剪出一个最大的圆，这个圆的面积是多少平方厘米．
<gadget id="calculator">20 / 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>