The minute hand of a quartz clock is 9 cm long, from 8:20 to 8:40, how many square centimeters does the minute hand sweep?
一个石英钟的分针长9厘米，从8：20走到8：40，这根分针扫过的面积是多少平方厘米？
<gadget id="calculator">9 ** 2</gadget>
<output>81</output>

<gadget id="calculator">20 / 60</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">3.14 * 81 * (1/3)</gadget>
<output>84.78</output>

<result>84.78</result>