There is a wall clock, the minute hand is 50 cm long, how many square centimeters is the area swept by the tip of the needle when the minute hand makes one revolution?
有一个挂钟，分针长50厘米，分针走一圈，针尖转一周扫过的面积是多少平方厘米．
<gadget id="calculator">50 ** 2</gadget>
<output>2_500</output>

<gadget id="calculator">3.14 * 2_500</gadget>
<output>7_850</output>

<result>7_850</result>