From 1 o'clock to 4 o'clock, how many square centimeters does the hour hand sweep? (hour hand length 20cm)
从1点到4点，时针扫过的面积为多少平方厘米？(时针长20cm)
<gadget id="calculator">20 ** 2</gadget>
<output>400</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">3.14 * 400 * (1/4)</gadget>
<output>314</output>

<result>314</result>