A cylinder whose base radius is 2 decimeters and whose height is 4 decimeters, what is its lateral area?
一个圆柱的底面半径是2分米，高是4分米，它的侧面积是多少．
<gadget id="calculator">2 * 3.14 * 2 * 4</gadget>
<output>50.24</output>

<result>50.24</result>