A wall clock, the hour hand is 40 cm long, how many square centimeters does the hour hand sweep after a day and night?
一个挂钟，时针长40厘米，经过一昼夜，时针扫过的面积是多少平方厘米？
<gadget id="calculator">40 ** 2</gadget>
<output>1_600</output>

<gadget id="calculator">3.14 * 1_600 * 2</gadget>
<output>10_048</output>

<result>10_048</result>