A cylindrical water pipe with an inner diameter of 20 cm and a flow rate of water in the pipe is 40 cm per second, how many cubic centimeters of water flow per second
一根圆柱形水管，内直径是20厘米，水在管内的流速是每秒40厘米，每秒流过的水是多少立方厘米
<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<gadget id="calculator">10 ** 2</gadget>
<output>100</output>

<gadget id="calculator">3.14 * 100 * 40</gadget>
<output>12_560</output>

<result>12_560</result>