clock, the hour hand is 9 cm long, and the hour hand moves from 2 to 6, how many square centimeters does the hour hand sweep?
一个钟，时针长9厘米，时针2走到6，时针所扫过的地方有多少平方厘米．
<gadget id="calculator">9 ** 2</gadget>
<output>81</output>

<gadget id="calculator">120 * 3.14 * 81</gadget>
<output>30_520.8</output>

<gadget id="calculator">30_520.8 / 360</gadget>
<output>84.78</output>

<result>84.78</result>