cylindrical pipe with an inner diameter of 20 cm and a water velocity of 50 cm per second is the volume of water flowing in cubic centimeters per second.
一根圆柱形管道，内直径为20厘米，水流速度是每秒50厘米，每秒流过的水的体积是多少立方厘米．
<gadget id="calculator">20 / 2</gadget>
<output>10</output>

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

<gadget id="calculator">3.14 * 100 * 50</gadget>
<output>15_700</output>

<result>15_700</result>