The minute hand of the clock is 9cm long. It runs from 8:00 to 8:20. What is the area swept by the minute hand?
时钟的分针长9cm，它从8点整走到8点20分，这个分针扫过的面积为多少．
<gadget id="calculator">20 / 60</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">3.14 * 9 * 9 * (1/3)</gadget>
<output>84.78</output>

<result>84.78</result>