A cylinder is made from a rectangular iron sheet with a length of 4.5 decimeters and a width of 1 decimeter. What is the maximum lateral area of this cylinder? (interface not counted)
用一张长4.5分米，宽1分米的长方形铁皮制成一个圆筒，这个圆柱的侧面积最多是多少平方分米．(接口处不计)
<gadget id="calculator">4.5 * 1</gadget>
<output>4.5</output>

<result>4.5</result>