A circular granary has a bottom radius of 3 meters. What is the floor area of this granary in square meters?
一个圆形粮仓，底面半径是3米，问这个粮仓的占地面积是多少平方米？
<gadget id="calculator">3 ** 2</gadget>
<output>9</output>

<gadget id="calculator">3.14 * 9</gadget>
<output>28.26</output>

<result>28.26</result>