There is a circular clock, the minute hand is 30 cm long, what is the area swept by the minute hand in one hour?
有一个圆形钟表，分针长30厘米，一小时后，分针扫过的面积是多少平方分米．
<gadget id="calculator">30 ** 2</gadget>
<output>900</output>

<gadget id="calculator">900 / 100</gadget>
<output>9</output>

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

<result>28.26</result>