If a rectangle with a length of 20 cm and a width of 10 cm is rotated around its length, a cylinder is obtained. What is the volume of this cylinder?
将一个长20厘米，宽10厘米的长方形以长为轴旋转一周，得到一个圆柱，这个圆柱的体积是多少．
<gadget id="calculator">10 ** 2</gadget>
<output>100</output>

<gadget id="calculator">3.14 * 100 * 20</gadget>
<output>6_280</output>

<result>6_280</result>