A cylinder has a radius of 2 cm and a height of 1 m. Cut vertically downward along the diameter of the upper bottom, what is the area of one of the cut surfaces in cm**2.
一个圆柱体半径2cm，高1m．沿上底直径垂直向下切开，其中的一个切面面积是多少cm**2．
<gadget id="calculator">2 * 2 * 1 * 100</gadget>
<output>400</output>

<result>400</result>