Use a piece of rectangular paper with a length of 18cm and a width of 5cm to form a cylinder, what is the lateral area in cm**2.
用一张长18cm，宽5cm的长方形纸围成一个圆柱，侧面积是多少cm**2．
<gadget id="calculator">18 * 5</gadget>
<output>90</output>

<result>90</result>