The radius of the base of a cylinder is 4 decimeters and the height is 5 decimeters, what is the lateral area?
一个圆柱体底面半径是4分米，高是5分米，侧面积是多少．
<gadget id="calculator">3.14 * 4 * 2 * 5</gadget>
<output>125.6</output>

<result>125.6</result>