A rectangular plank is 45 meters long and 20 meters wide. Please cut out the largest circle on this board, what is the area of the circle in square meters?
一块长方形木板，长45米，宽20米．请你在这块木板上截下一个最大的圆，圆的面积是多少平方米？
<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>